Test Transistors with Multimeter and Semiconductor Analyzer

This article includes step-by-step tests on a variety of transistors:

  • NPN
  • PNP
  • Matched pair transistors
  • Complimentary transistor pairs
  • Signal vs switching transistors
  • Silicon
  • Germanium
  • Darlington
  • Devices with unexpected pinouts according to the datasheet
  • Special tools for handling SMD devices
  • Power transistors with and without shunt resistors and damper diodes
  • Known good
  • Known bad
  • Leaky
  • Unknown TO-92 part
  • 70-year-old pre-production junction transistor
  • Devices with unexpected DMM or semiconductor analyzer results

The two figures below show the various types of transistors tested in this article. Most of the package styles shown in the figure below (left) help verify pinouts for emitter (E), collector (C), and base (B). But TO-92 packages are not standardized. Refer to the datasheet/manufacturer for TO-92 devices. Even then a DMM or Analyzer test should be used to verify pin-outs from a new batch of devices. See BC517 tests below for an example where DMM test was required because the manufacturer’s datasheet was not correct for my part.

Table of Contents

DMM and Semiconductor Analyzer Test Methodology

I present a detailed test methodology for 14 different BJT transistors in this article. Here I summarize my lessons learned during this process.

  • There are four basic tests required for transistors in practical troubleshooting: gain, leakage, breakdown, and switching time. Gain and leakage are tested with DMM. Breakdown, or knee in curve traces are tested with a semiconductor analyzer. Switching time will be reviewed at a later time.
  • Place DMM into diode check mode so enough current can be supplied to transistor legs under test for forward voltage junction readings. This will confirm whether the device is NPN or PNP.
  • The DMM ohmmeter may be used instead of the diode mode. But some ohm scales may give unexpected results. Specifically, if the ohmmeter’s test voltage is below ~650mV (for silicon) and ~300mV for germanium then forward bias issues will result. Your meter might read OL for a good device. While some devices in this article require the DMM’s ohm scales for testing built-in base−emitter shunt resistors: TIP147 and NTE89
  • The DMM (ohm or diode) will not work with the NTE89 Transistor. Also the semiconductor analyzer will not work. To solve the higher current requirement for testing some devices a constant current DC power supply can be used. See the discussion related to the NTE89 Power Transistor in this article.
  • For unknown devices determine forward voltage readings between one common pin (base) and the emitter/collector pins (junctions). If the base is positive then the device is NPN, otherwise, it is PNP.
  • The BJT emitter region is more heavily doped than the collector. As a result, the emitter-base junction will have a slightly greater forward voltage drop (using the DMM diode check function) than the collector-base junction. Yet one device presented in this article violates this rule: M1752
  • Orient the transistor in a consistent manner when testing each pin with a DMM. Consistency can be a big help while keeping track of device emitter, collector, base, pins 1 to 3, and positive/negative DMM cables.
  • Use the part’s datasheet where possible, but use your DMM to verify pinouts. One device in this article used an alternate pinout with respect to the datasheet: BC517
  • A semiconductor analyzer offers a range of parameters not available to a DMM.
  • SMD transistor devices offer a unique challenge based on their small size. I present tools to help test these devices: MMBT5551 NPN SOT-23, PTZ2222a NPN SOT-223, and NST45010MW6T1G PNP Matched Pair SOT-363. Where SOT stands for small outline transistor.
  • There are several options to test the hFE (DC current gain or β) parameter:
    • Use a semiconductor analyzer as shown in this article
    • Use the built-in test socket available on some low-cost DMMs
    • Parts commonly available (breadboard, two resistors, and 9-volt power source) can be used with transistor under test along with DMM to calculate hFE: see my related article Testing Transistor DC Gain (hFE) in My Lab
    • See the “Test Transistor Gain” sections within each transistor tested below for go-no-go gain tests using a DMM

Small Signal vs Small Switching Transistors

Small Switching Transistors

Switching transistors tend to have a lower DC gain (hFE) value from 10 to 200. They also tend to have a wider range of collector current IC ratings which range from 10 mA to 1000 mA. Older switching transistors likely will include their turn on TON (28 ns for 2N3638) and turn off TOFF (78 ns for 2N3638) times in their datasheet. While newer parts will have a switching characteristics section in their datasheet such as the 2N3906 general purpose transistor (TON 65 ns and TOFF 300 ns). Some datasheets don’t include TON and TOFF. Instead, they would have td (delay time) and tr (rise time) where TON = td + tr. Similarly, instead of TOFF the device datasheet would list ts (storage time) and tr (fall time) where TOFF = ts + tr. See Lecture-10: BJT Switching Characteristics, Small Signal Model for details.

Small Signal Amplifier Transistors

Amplifier transistors have a DC gain (hFE) value from 10 to 500. Their collector’s current IC rating ranges from 80 mA to 600 mA. These transistors will include a small-signal characteristics section in their datasheet, such as the 2N3906 general purpose transistor.

TO-92 Silicon Transistors

2N3906 PNP Transistor with Known Pin-out

Click the image to view PDF Datasheet for silicon PNP 2N3906 transistor.

Test working 2N3906 TO-92 PNP silicon transistor with known pinouts.

Test 2N3906 VBE forward biased voltage drop

Probe base (negative lead) to the emitter (positive lead) using the DMM’s diode mode.

Test 2N3906 VBE forward biased voltage drop.

Test result in the .5 to 1 VDC range indicates transistor made of silicon.

Fluke 289 DMM diode mode result.

VBE test result indicates a transistor made of silicon for a working transistor.

Test 2N3906 transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE (above).

Test 2N3906 transistor go/no-go gain.
Fluke 289 DMM diode mode result.

DMM reading will be noticeably lower than VBE test result above for a working transistor.

Test 2N3906 VCB forward biased voltage drop

Probe base (negative lead) to the collector (positive lead) using DMM’s diode mode.

Test 2N3906 VCB forward biased voltage drop.
Fluke 289 DMM diode mode result.

Test results should be slightly lower than the VBE value for a working transistor. The lower reading verifies probes are on base and collector.

Test 2N3906 VEC for leakage

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test 2n3906 VEC for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading in diode test mode should display OL; i.e., the transistor has no leakage between emitter and collector.

Test 2N3906 VCE for leakage

Probe collector (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test 2N3906 VCE for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading in diode test mode should display OL; i.e., the transistor has no leakage between collector and emitter.

Verify 2N3906 DMM Tests using Atlas DCA Pro Semiconductor Analyzer

Results from DCA Pro model DCA75 Test and Ic /Vce Curve Trace for 2N3906.

Click the image to enlarge.
Click the image to enlarge.

2N3904 TO-92 NPN Silicon Transistor

Click the image to view the PDF datasheet for silicon NPN 2N3904 transistor.

Test working 2N3904 TO-92 NPN silicon transistor with known pinouts.

Test 2N3904 VBE forward biased voltage drop

Probe base (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test 2N3904 VBE forward biased voltage drop.

Test result in the .5 to 1 VDC range indicates transistor made of silicon.

Fluke 289 DMM diode mode result.

VBE test result indicates a transistor made of silicon for a working transistor.

Test 2N3904 transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE (above).

Test 2N3904 transistor go/no-go gain.
Fluke 289 DMM diode mode result.

DMM reading will be noticeably lower than the VBE test result above for a working transistor.

Test 2N3904 VCB forward biased voltage drop

Probe base (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test 2N3904 VCB forward biased voltage drop.
Fluke 289 DMM diode mode result.

Test results should be slightly lower than the VBE value for a working transistor. The lower reading verifies probes are on collector and base.

Test 2N3904 VEC for leakage

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test 2N3904 VEC for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading in diode test mode should display OL; i.e., the transistor has no leakage between emitter and collector.

Test 2N3904 VCE for leakage

Probe collector (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test 2N3904 VCE for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading in diode test mode should display OL; i.e., the transistor has no leakage between collector and emitter.

Verify 2N3904 DMM Tests using Atlas DCA Pro Semiconductor Analyzer

Results from DCA Pro model DCA75 Test and Ic /Vce Curve Trace for 2N3904

Click the image to enlarge.
Click the image to enlarge.

Known Bad 2N3904 Transistor

Click the image to view the PDF datasheet for silicon NPN 2N3904 transistor.

Refer to testing a known good 2N3904 above to compare bad transistor with typical DMM values for VBE, VBE gain test, and VCB.

Test bad 2N3904 VBE forward biased voltage drop

Probe base (positive lead) to the emitter (negative lead) using the DMM’s diode mode.

Test bad 2N3904 VBE forward biased voltage drop.
Fluke 289 DMM diode mode result.

The test result shows a short between base and emitter for this bad transistor.

Test bad 2N3904 transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE (above).

Test bad 2N3904 transistor go/no-go gain.
Fluke 289 DMM diode mode result.

DMM reading has not changed. Indicating there is no gain available with this bad transistor.

Test bad 2N3904 VCB forward biased voltage drop

Probe base (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test bad 2N3904 VCB forward biased voltage drop.
Fluke 289 DMM diode mode result.

The test result is too low. Another indication of a bad transistor.

Verify bad 2N3904 DMM Tests using Atlas DCA Pro Semiconductor Analyzer

Results from DCA Pro model DCA75 test for bad 2N3904 transistor showing base to emitter shorted. The empty box is shown in the figure below right on purpose as there are no results to plot there.

DCA Pro model DCA75 results for bad transistor.

BC517 TO-92 Silicon NPN Darlington Transistor

Click the image to view the PDF datasheet for the silicon NPN Darlington BC517 transistor. Note that the datasheet pin-outs for Emitter and Collector are reversed for my specific device. Don’t assume the datasheet pinout will be correct for your device.
DCA Pro shows that the datasheet pin-out for this BC517 part has the Emitter and Collector pins reversed.

In this example, the small-signal Darlington part datasheet shows the emitter (E) and collector (C) pins in reverse compared to the actual device under test here. Don’t trust the datasheet. The DMM tests are presented here to verify the pinouts.

Test BC517 VBE forward biased voltage drop

Probe base (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test BC517 VBE forward biased voltage drop.
Fluke 289 DMM diode mode result.

VBE test results in the 1 to 1.5 VDC range indicate the transistor is made of silicon and has two emitter junctions in series for a working transistor.

Test BC517 transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE (above).

Test BC517 transistor go/no-go gain.
Fluke 289 DMM diode mode result.

DMM reading will be slightly lower than the VBE test result above for a working transistor.

Test BC517 VCB forward biased voltage drop

Probe base (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test BC517 VCB forward biased voltage drop.
Fluke 289 DMM diode mode result.

Like most Darlington transistors, the collector terminal is laced with a resistor to limit the flow of current. So VCB test results will be much lower than the VBE value for a working transistor.

Test BC517 VEC for leakage

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test BC517 VEC for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the VEC DMM reading should be OL indicating no leakage.

Test BC517 VCE for leakage.

Probe collector (positive lead) to the emitter (negative lead) using DMM’s diode mode

Test BC517 VCE for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the VCE DMM reading should be OL indicating no leakage.

Verify BC517 DMM Tests using Atlas DCA Pro Semiconductor Analyzer

By default, the DCA Pro automatically sets Ib from 0.0 uA to 0.0 uA to generate 5 traces because of the very high hFE gain for this Darlington transistor. This setup results in 5 curves all on the Ic = 0 as flat overlapping lines.
As a workaround (as shown below), change the Ib parameters from 0.0 uA for the start, and to 0.1 uA for the end, to get 5 traces looking like a typical set of curves (lower right figure). The actual Ib values for the 5 traces: 0.02, 0.04, .06, .08, .1 *

I note also the interesting and noisy results with one of the Darlingtons (BC517). That’s purely because the gain is so high that it is extremely difficult to control the tiny base currents to obtain a suitable curve. The base current control is getting close to the minimum resolution possible and therefore the graph becomes noisy.

See the reply from Jeremy Siddons at the end of the post for more details.
Click the image to enlarge.
Click the image to enlarge.

Unknown TO-92 Transistor

Test Unknown TO-92 Transistor Using DMM

Unknown part with pins numbered for test reference.

Label the three leads of the transistor with the numbers 1, 2, and 3.

Record the DMM diode readings for each permutation (order is important) of the three pins taken 2 at a time.

If the transistor is good there will be 2 tests with VDC readings from the 6 permutations that will indicate:

  • VBE forward voltage drop
  • VCB reverse voltage drop that is slightly lower than VBE

DMM Diode Mode test results for each pin combination for the unknown part:

  • Pins 1(+) to 2(-): 0.6845 VDC
  • Pins 2(+) to 1(-): OL
  • Pins 1(+) to 3(-): OL
  • Pins 3(+) to 1(-): OL
  • Pins 2(+) to 3(-): OL
  • Pins 3(+) to 2(-): 0.6805 VDC

The conclusion from the test values above:

  • Pin 2 is the base because this pin is common to both tests with a voltage reading.
  • Pin 1 is the emitter because pin-1-to-base has the higher voltage drop (VBE).
  • Pin 3 is the collector because pin-3-to-base has a lower voltage drop (VCB).
  • The transistor is a PNP type because the base must be negative to cause the current to flow through the emitter and collector. NPN transistors would have a base that is a positive voltage.
  • Transistor is made from silicon because the VBE and VCB voltage drops are in the range of 0.5 and 1.0 VDC. Germanium transistors would have lower voltage drops in the range of 0.2 and 0.3 VDC. While, darlington transistors would have a higher voltage drop in the 1.0 to 1.5 VDC range.

Additional notes on testing an unknown transistor:

In some cases, there may be more pin combinations with a voltage reading (not just two as in the test results shown in this case). The cause may be based on a good device with internal resistor/diode components as demonstrated in some of the transistors tested in this post. A bad device may show a voltage reading on other pins as well. Also consider voltage differences for Ge, Si, and Darlington designs. And of course, the three-pin device may not even be a BJT transistor such as a FET, unijunction transistor, or something else.

Verify Unknown Part using Atlas DCA Pro Semiconductor Analyzer

Confirmation of pin assignments and semiconductor material for the unknown transistor.

Results from DCA Pro model DCA75 Test and Ic /Vce Curve Trace for unknown the PNP silicon transistor.

Click the image to enlarge.
Click the image to enlarge.

Convert the unknown transistor data into a manufacturer part number

Newark (among others) offers a BJT selection guide located here: https://www.newark.com/c/semiconductors-discretes/transistors/bipolar-transistors/single-bipolar-junction-transistors-bjt

Use the selections offered by Newark with the data gathered on the unknown transistor:

  • Initially, there are 3,484 parts found (at the time when this post was created)
  • Select “Suitable for New Designs”: 3,413 parts found
  • Select “PNP”: 1,354 parts found
  • Select “TO-92 Case Style”: 44 parts found
  • Select “100 hFE DC Current Gain” used here as just a ballpark value: 7 parts found
  • Of the 7 parts found for my needs, I would select: 2N3906
Click the image to see all 7 results from the Newark part search as a PDF.

Now the unknown part has a proposed manufacturer’s part name for use in new designs or as a repair replacement.

SMD Silicon Transistors.

MMBT5551 SOT-23 NPN Silicon Transistor

Click image to view PDF datasheet for SOT-23 MMBT5551 (incl. 2N5551) transistor.

Test working SOT-23 -3 NPN Ssilicon transistor with known pinouts.

Prepare the tiny SMD STO-23 package for testing. I used this nearly foolproof spring-loaded test adapter model PCA23 by PEAK Electronics Design Ltd for easy connectivity to my DMM.

Note: I wrote the pin assignments (B for the base, E for the emitter, and C for the collector) on the adapter since the SOT-23-3 form factor is mostly standardized – unlike TO-92 transistors.

Test MMBT5551 VBE forward biased voltage drop

Probe base (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test MMBT5551 VBE forward biased voltage drop.

Test result in the .5 to 1 VDC range indicates transistor made of silicon.

Fluke 289 DMM diode mode result.

VBE test result indicates a transistor made of silicon for a working transistor.

Test MMBT5551 transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE (above).

Test MMBT5551 go/no-go transistor gain.
Fluke 289 DMM diode mode result.

DMM reading will be noticeably lower than the VBE test result above for a working transistor.

Test MMBT5551 VCB forward biased voltage drop

Probe base (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test VCB forward biased voltage drop.
Fluke 289 DMM diode mode result.

Test results should be slightly lower than the VBE value for a working transistor. The lower reading verifies probes are on base and collector.

Test MMBT5551 VEC for leakage

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test VEC for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL indicating no leakage.

Test MMBT5551 VCE for leakage

Probe collector (positive lead) to the emitter (negative lead) using the DMM’s diode mode.

Test VCE for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL indicating no leakage.

Verify MMBT5551 DMM Tests using Atlas DCA Pro Semiconductor Analyzer

Results from DCA Pro model DCA75 Test and Ic /Vce Curve Trace for MMBT5551 (incl. 2N5551) Transistor.

Click the image to enlarge.
Click the image to enlarge.

PTZ2222a SOT-223 NPN Silicon Transistor

Click image to view PDF datasheet for SOT-223 silicon PTZ2222a (incl. 2N2222a) transistor.

Test working SOT-223 silicon transistor with known pinouts.

I used SMD tweezer test leads to perform these tests. They are inexpensive and fit most any DMM.

Test PTZ2222a VBE forward biased voltage drop

Probe base (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test PTZ2222a VBE forward biased voltage drop.
Fluke 289 DMM diode mode result.

VBE test results in the .5 to 1 VDC range indicates transistor made of silicon for a working transistor.

Test PTZ2222a transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE (above).

Test PTZ2222a transistor go/no-go gain.
Fluke 289 DMM diode mode result.

DMM reading will be noticeably lower than the VBE test result above for a working transistor.

Test PTZ2222a VCB forward biased voltage drop

Probe base (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test PTZ2222a VCB forward biased voltage drop.
Fluke 289 DMM diode mode result.

Test results should be slightly lower than the VBE value for a working transistor. The lower reading verifies probes are on base and collector.

Test PTZ2222a VEC for leakage

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test PTZ2222a VEC for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL indicating no leakage.

Test PTZ2222a VCE for leakage

Probe collector (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test PTZ2222a VCE for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL for no leakage.

Verify PTZ2222a DMM Tests using Atlas DCA Pro Semiconductor Analyzer

Results from DCA Pro model DCA75 Test and Ic /Vce Curve Trace for PTZ2222a (incl. 2N2222a) transistor.

Click the image to enlarge.
Click the image to enlarge.

NST45010MW6T1G SOT-363 PNP Dual Matched Silicon Transistors

Click image to view PDF datasheet for SOT-363 silicon NST45010MW6T1G transistor.

Test working SOT-363 PNP silicon dual matched transistors with known pinouts.

Prepare the tiny SMD TO-363 package for testing. I used a SOT363 DIP Breakout Board from Dreyer Electronics (purchased from Amazon).

Test SMD SOT-323 NST45010MW6T1G dual-matched transistor pair using Atlas DCA Pro Semiconductor Analyzer

Results for Q1 transistor within NST45010MW6T1G.

Click the image to enlarge.
Click the image to enlarge.

Results for Q2 transistor within NST45010MW6T1G.

Click the image to enlarge.
Click the image to enlarge.

Results for Q1 and Q2 transistors superimposed within NST45010MW6T1G. Note how closely the two transistors match each other.

Q1 and Q2 traces are superimposed. Click the image to enlarge.

TO-18 / TO-5 Silicon / Germanium Transistors

2N2369 TO-18 NPN Silicon Transistor

Click image to view PDF datasheet for NPN silicon 2N2369 transistor.

Test working TO-5 NPN silicon transistor with known pinouts.

Test 2N2369 VBE forward biased voltage drop

Probe base (positive lead) to the emitter (negative lead) using the DMM’s diode mode.

Test 2N2369 VBE forward biased voltage drop.
Fluke 289 DMM diode mode result.

VBE test result in the .5 to 1 VDC range indicates transistor made of silicon for a working transistor.

Test 2N2369 transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE (above).

Test 2N2369 transistor go/no-go gain.
Fluke 289 DMM diode mode result.

DMM reading will be noticeably lower than the VBE test result above for a working transistor.

Test 2N2369 VCB forward biased voltage drop

Probe base (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test 2N2369 VCB forward biased voltage drop.
Fluke 289 DMM diode mode result.

Test results should be slightly lower than the VBE value for a working transistor. The lower reading verifies probes are on base and collector.

Test 2N2369 VEC for leakage

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test 2N2369 VEC for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL indicating no leakage.

Test 2N2369 VCE for leakage

Probe collector (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test 2N2369 VCE for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL for no leakage.

Verify 2N2369 DMM Tests using Atlas DCA Pro Semiconductor Analyzer

Results from DCA Pro model DCA75 Test and Ic /Vce Curve Trace for 2N2369.

Click the image to enlarge.
Click the image to enlarge.

2N388 TO-5 NPN Germanium Transistor

Click image to view PDF data parameters for germanium NPN 2N388 transistor.
This old RCA 2N388 part can still be used in a circuit if tested first.

Test working 2N388 TO-5 NPN germanium transistor with known pinouts.

Test 2N388 VBE forward biased voltage drop

Probe base (positive lead) to the emitter (negative lead) using the DMM’s diode mode.

Test 2N388 VBE forward biased voltage drop.
Fluke 289 DMM diode mode result.

Test result in the .2 VDC range indicates a transistor made of germanium for a working transistor.

Test 2N388 transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE (above).

Test 2N388 transistor go/no-go gain.
Fluke 289 DMM diode mode result.

DMM reading will be noticeably lower than the VBE test result above for a working transistor.

Test 2N388 VCB forward biased voltage drop

Probe base (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test 2N388 VCB forward biased voltage drop.
Fluke 289 DMM diode mode result.

Test results should be slightly lower than the VBE value for a working transistor. The lower reading verifies probes are on base and collector.

Test 2N388 VEC for leakage

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test 2N388 VEC for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL representing no leakage.

Test 2N388 VCE for leakage

Probe collector (positive lead) to the emitter (negative lead) using the DMM’s diode mode.

Test 2N388 VCE for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL indicating no leakage.

Verify 2N388 DMM Tests using Atlas DCA Pro Semiconductor Analyzer

Results from DCA Pro model DCA75 Test and Ic /Vce Curve Trace for 2N388

Click the image to enlarge.
Click the image to enlarge.

2N388 TO-5 NPN Leaky Germanium Transistor

Click image to view PDF data parameters for germanium NPN 2N388 transistor.

Test leaky 2N388 TO-5 NPN germanium transistor with known pinouts.

Test leaky 2N388 VBE forward biased voltage drop

Probe base (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test leaky 2N388 VBE forward biased voltage drop.
Fluke 289 DMM diode mode result.

Test result in the .2 VDC range indicates transistor made of germanium.

Test leaky 2N388 transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE (above).

Test leaky 2N388 transistor go/no-go gain.
Fluke 289 DMM diode mode result.

DMM reading will be noticeably lower than the VBE test result above.

Test leaky 2N388 VCB forward biased voltage drop

Probe base (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test leaky 2N388 VCB forward biased voltage drop.
Fluke 289 DMM diode mode result.

The test results should be slightly lower than the VBE value. The lower reading verifies probes are on base and collector.

Test leaky 2N388 VEC for leakage

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test leaky 2N388 VEC for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL indicating no leakage. While this unit clearly shows excessive leakage and should not be used in a typical circuit.

Test leaky 2N388 VCE for leakage

Probe collector (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test leaky 2N388 VCE for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL indicating no leakage. While this unit clearly shows excessive leakage and should not be used in a typical circuit.

Verify excessively leaky 2N388 DMM tests using Atlas DCA Pro Semiconductor Analyzer

Results from DCA Pro model DCA75 Test and Ic /Vce Curve Trace for excessively leaky 2N388. The curves never flatten as a result of the large IC leakage.

Click the image to enlarge.
Click the image to enlarge.

2N414 TO-5 PNP Germanium Transistor

Click image to view PDF datasheet for germanium PNP 2N414 transistor

Test working 2N414 TO-5 PNP germanium transistor with known pinouts.

Test 2N414 VBE forward biased voltage drop

Probe base (negative lead) to the emitter (positive lead) using DMM’s diode mode.

Test 2N414 VBE forward biased voltage drop.
Fluke 289 DMM diode mode result.

Test result in the .2 VDC range indicates a transistor made of germanium.

Test 2N414 transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE (above).

Test 2N414 transistor go/no-go gain.
Fluke 289 DMM diode mode result.

DMM reading will be noticeably lower than the VBE test result above.

Test 2N414 VCB forward biased voltage drop

Probe base (negative lead) to the collector (positive lead) using the DMM’s diode mode.

Test 2N414 VCB forward biased voltage drop.
Fluke 289 DMM diode mode result.

The test results should be slightly lower than the VBE value. The lower reading verifies probes are on base and collector.

Test 2N414 VEC for leakage

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test 2N414 VEC for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL indicating no leakage.

Test 2N414 VCE for leakage

Probe collector (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test 2N414 VCE for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL indicating no leakage.

Verify 2N414 DMM Tests using Atlas DCA Pro Semiconductor Analyzer

Results from DCA Pro model DCA75 Test and Ic /Vce Curve Trace for 2N414.

Click the image to enlarge.
Click the image to enlarge.

Pre-Production / Antique Transistor

Test M1752 NPN Prototype (1951) Junction Germanium Transistor

Click image to view PDF “datasheet” for this individual germanium NPN M1752 transistor
M1752 NPN germanium junction transistor
M1752 NPN germanium junction transistor

Presented here is an antique pre-production M1752 germanium junction transistor that is 70 years old as of the publishing of this article. A modern 2N3904 transistor is shown for comparison. Click on the “PDF Data on Envelope” link above to view the data supplied on the original envelope used to package this M1752 part.

This device made history in 1951 with the press release “GORDON TEAL GROWS LARGE SINGLE CRYSTALS OF GERMANIUM AND WORKS WITH MORGAN SPARKS TO FABRICATE AN N-P-N JUNCTION TRANSISTOR.” Together with this press release, a limited number of development models of the Bell Telephone Labs M1752 were made for preliminary study in several possible circuit applications. Biophysics Lab is lucky enough to have acquired one from eBay, sourced by the Southwest Museum of Engineering Communications and Computation (http://www.smecc.org/). Also see the link in the FAQ section at the end of this article: The K.D. Smith Collection By Ed Sharpe.

Test M1752 VBE forward biased voltage drop

Probe base (negative lead) to the emitter (positive lead) using the DMM’s diode mode.

Test M1752 VBE forward biased voltage drop.
Fluke 289 DMM diode mode result.

Test result in the .2 VDC range indicates a transistor made of germanium.

Test M1752 transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE (above).

Test M1752 transistor go/no-go gain.
Fluke 289 DMM diode mode result.

DMM reading will be noticeably lower than the VBE test result above.

Test M1752 VCB forward biased voltage drop

Probe base (negative lead) to the collector (positive lead) using DMM’s diode mode.

Test M1752 VCB forward biased voltage drop.
Fluke 289 DMM diode mode result.

For modern BJT’s test results should be slightly lower than the VBE value. Yet for preproduction devices the VCB is in fact higher than VBE. See Figure 16-2 p. 130 in “Analog Circuit Design” by Jim Williams where he points out that early junction transistors had emitter junction larger than the collector. Modern transistors reversed the size of E and C junctions where the collector is larger. See Figure 16-3 p.131 in the same book. So results shown here are correct for collector-base.

Test M1752 VEC for leakage

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode. Take care not to short the thin flexible leads during the test.

Test M1752 VEC for leakage.

For a good transistor, the DMM reading should be OL indicating no leakage.

Test M1752 VCE for leakage

Probe collector (positive lead) to the emitter (negative lead) using the DMM’s diode mode.

Test M1752 VCE for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL indicating no leakage.

Verify M1752 DMM Tests using Atlas DCA Pro Semiconductor Analyzer

Results from DCA Pro model DCA75 Test and Ic /Vce Curve Trace for M1752.

On the subject of the M1752, it looks like the VCEO (the maximum allowable voltage that can be applied from the collector to the emitter of a transistor before it becomes damaged or destroyed) of the device means that it is starting to breakdown as the VCE is getting bigger. This causes an avalanche and therefore the VCE actually drops even though the voltage across the load and the transistor is increasing.

See the full comment from Jeremy Siddons at the end of the post for more details.
Semiconductor analyzer setup for M1752 transistor.
Click the image to enlarge.
Click the image to enlarge.

TO-3 / TO-66 Silicon Power Transistors

2SB554 TO-3 Silicon PNP Transistor

Complimentary type to NPN 2SD424 (see test results below).

Click image to view PDF datasheet for silicon PNP 2SB544 transistor.

Test 2SB554 VBE forward biased voltage drop

Probe base (negative lead) to the emitter (positive lead) using the DMM’s diode mode.

Test PNP 2SB554 VBE forward biased voltage drop.
Fluke 289 DMM diode mode result.

Test result in the .5 to 1 VDC range indicates transistor made of silicon. Note: results are similar for all the single emitter junction (not Darlington) silicon transistors tested – including a wide selection of package sizes TO-92, TO-5, TO-3 etc…

Test 2SB554 transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE (above).

Test PNP 2SB554 transistor go/no-go gain.
Fluke 289 DMM diode mode result.

DMM reading will be noticeably lower than the VBE test result above.

Test 2SB554 VCB forward biased voltage drop

Probe base (negative lead) to the collector (positive lead) using the DMM’s diode mode.

Test PNP 2SB554 VCB forward biased voltage drop.
Fluke 289 DMM diode mode result.

Test results should be slightly lower than the VBE value. The lower reading verifies probes are on base and collector.

Test 2SB554 VEC for leakage

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test PNP 2SB554 VEC for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL indicating no leakage.

Test 2SB554 VCE for leakage

Probe collector (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test PNP 2SB554 VCE for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL indicating no leakage.

Verify 2SB554 DMM Tests using Atlas DCA Pro Semiconductor Analyzer

Click the image to enlarge.
Click the image to enlarge.

2SD424 TO-3 Silicon NPN Power Transistor

Complimentary type to PNP 2SB544 (see test results above).

Click image to view PDF datasheet for silicon NPN 2SD424 transistor

Test 2SD424 VBE forward biased voltage drop

Probe base (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test NPN 2SD424 VBE forward biased voltage drop
Fluke 289 DMM diode mode result.

Test result in the .5 to 1 VDC range indicates transistor made of silicon.

Test 2SD424 transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE (above).

Test NPN 2SD424 transistor go/no-go gain.
Fluke 289 DMM diode mode result.

DMM reading will be noticeably lower than the VBE test result above.

Test 2SD424 VCB forward biased voltage drop

Probe base (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test NPN 2SD424 VCB forward biased voltage drop
Fluke 289 DMM diode mode result.

The test result should be slightly lower than the VBE value. The lower reading verifies probes are on base and collector. In this case, the difference is so small you may have to refer to the datasheet or semiconductor analyzer results (see below) to be sure.

Test 2SD424 VEC for leakage

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test NPN 2SD424 VEC for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL indicating no leakage.

Test 2SD424 VCE for leakage

Test NPN 2SD424 VCE for leakage.

Probe collector (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL for no leakage.

Verify 2SD424 DMM Tests using Atlas DCA Pro Semiconductor Analyzer

Results from DCA Pro model DCA75 Test and Ic /Vce Curve Trace for 2SD424

Click the image to enlarge.
Click the image to enlarge.

Compare NPN 2SD424 with PNP 2SB554 Complimentary Pair transistors using Atlas DCA Pro Semiconductor Analyzer

See individual tests for each transistor 2SD424 and 2SB554 above. Note the difference in gain, hFE: 258 for the NPN 2SD424 device and 132 for the PNP 2SB544 device.

IC/ VCE curve traces superimposed using Atlas DCA Pro Semiconductor Analyzer

TIP147 TO-220 Silicon PNP Darlington Power Transistor

Click image to view PDF datasheet for silicon PNP TIP147 transistor.

Test working TO-220 PNP Darlington power silicon transistor that includes a parasitic diode and two performance-enhancing resistors with known pinouts. Referring to the schematic above: The two transistors are configured as a Darlington pair so that the emitter current of the first transistor becomes the base current of the second transistor. The two base-emitter shunt (or bypass) resistors limit the gain at low currents, reduce leakage current, increase transistor speed, and to reduce the chance of thermal runaway. While, the parasitic (or clamp) diode limits transients and noise.

Note on package styles: TiP147 comes in TO-247 (SOT-93), TO-218 and TO-220 packaging.

Test TIP147 VBE forward biased voltage drop

Probe base (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test PNP TIP147 VBE forward biased voltage drop.
Fluke 289 DMM diode mode result.

Test result in the .5 to 1 VDC range indicates transistor made of silicon.

Test TIP147 transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE (above).

Test PNP TIP147 transistor go/no-go gain.
Fluke 289 DMM diode mode result.

DMM reading will be noticeably lower than the VBE test result above.

Test TIP147 VCB forward biased voltage drop

Probe base (negative lead) to the collector (positive lead) using DMM’s diode mode.

Test PNP TIP147 VCB forward biased voltage drop.

The test results should be slightly lower than the VBE value. The lower reading verifies probes are on base and collector.

Test TIP147 parasitic diode

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test PNP TIP147 parasitic diode.
Fluke 289 DMM diode mode result.

TiP147 parasitic silicon diode is working when VF (forward voltage drop) is in the .5 to 1V range – as shown by DMM reading (left).

Test TIP147 shunt resistors

Probe base (positive lead) to the emitter (negative lead) using DMM’s kΩ mode. Note: the DMM continues to read lower kΩ values over time.

Test PNP TIP147 shunt resistors.
Fluke 289 DMM ohms min/max mode results.

TIP147 shunt resistors are working on this device. The ohms reading is similar to that described in the transistor’s schematic. Note the use of the meter’s averaging feature to track downward drift in value over a 6 minute perod.

Verify TIP147 DMM Tests using Atlas DCA Pro Semiconductor Analyzer

Results from DCA Pro model DCA75 Test and Ic /Vce Curve Trace for TIP147. The DCA Pro does not provide enough current to accurately test hFE or to complete all curves.

Click the image to enlarge.
Click the image to enlarge.

NTE89 TO-3 Silicon NPN Power Transistor

Click image to view PDF Datasheet for silicon NPN NTE98 power transistor

NTE89 device overview

The NTE89 Transistor, a.k.a. 2SD870, ECG89, or SK9119, was commonly used in the high voltage section of Cathode-ray tube (CRT) television sets such as the 1994 Samsung Model CT-509VA. I found that this device can not be fully tested using a DMM (Diode mode or Ohm scales) or the Atlas DCA Pro Semiconductor Analyzer because the current required by the Base-Emitter junction is too high: ~17 mA required instead of the 1 mA typically found in DMMs.

Read on for an alternative simple solution for testing this device’s VBE using a current limited power supply.

PHOTOFACT Technical Service Data, Samsung Model CT-509VA, Power Supply Schematic

Sorry, I’m not much of a fan of large, slow, low-beta
high-voltage BJTs. I know they can be very useful in
fluorescent ballast designs, etc. I suppose the days
of color-TV HOTs are coming to an end

Maker Pro discussion, Winfield Hill 2008

Test NTE89 VBE forward biased voltage drop using DMM Diode Test Mode

Probe base (positive lead) to emitter (negative lead) using DMM’s diode mode.

Test NPN NTE98 VBE forward biased voltage drop.
Fluke 289 DMM diode mode result.

Test result in the .5 to 1 VDC range indicates a typical transistor made of silicon. But this transistor fails using the simple DMM Diode Test Mode with 6V 1mA constant current source. The transistor is not bad (I actually purchased a new NTE89 to compare with my old unit with same DMM Diode Test Mode test result). The problem is that 1mA is not enough current to fully forward bias this transistor.

Test NTE89 VBE forward biased voltage drop using constant current power supply

In this test I connect the NTE89 to my Keysight E36313A power supply. The test setup is just like the DMM Diode Test Mode only I use a higher constant current of 17 mA. Connect power supply channel 2 positive terminal to the base, and the negative terminal to the emitter.

In the figure to the left I verify same test result from my DMM Diode Test Mode showing only a 0.047 V drop. In the middle figure I show a good VBE test result for my NTE89 unit based on a 0.591 V drop. The figure to the right shows the power supply test setup using LTSpice simulation for a typical silicon NPN transistor.

NTE89 VBE at 1 mA: Same test result as DMM Diode Test Mode.
NTE89 VBE at 17 mA: Verify working transistor with typical silicon junction voltage drop.
LTSpice simulation of FLUKE DMM Diode Test Mode. Schematic also shows the Keysight E36313A test setup for NTE89 VBE measurement in the two figures to the left.

Test NTE89 transistor go/no-go gain using constant current power supply

Short collector to base using the same probe setup as above for measuring VBE.

Voltage drop will be noticeably lower (0.585 V) than the VBE test result above (0.591 V).

Test NTE89 VCB forward biased voltage drop

Probe base (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test NPN NTE89 VCB forward biased voltage drop.

Unlike most BJT silicon transistors, the test result should be nearly the same as the VBE value.

Test NTE89 parasitic diode

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test NPN NTE89 parasitic diode.
Fluke 289 DMM diode mode result.

NTE89 transistor’s parasitic silicon diode is working. VF (forward voltage drop) is in the .5 to 1V range.

Test NTE89 shunt resistor

Probe base (negative lead) to the emitter (positive lead) using DMM’s Ohms mode. Note: the test produces similar results even if the polarity of test leads are reversed.

Test NPN NTE89 shunt resistor.
Fluke 289 DMM ohms result.

The NTE98 transistor’s shunt resistor is working for this device. The result is consistent with the schematic.

Unable to verify NTE89 DMM Tests using Atlas DCA Pro Semiconductor Analyzer

Results from DCA Pro produce test and I /V curve trace for NTE98 that look like a double diode structure in error. DCA Pro is outside the test range needed for this transistor. Yet these results may be used to identify and test other NTE98 transistors using the DCA Pro.

Click the image to enlarge.
Click the image to enlarge.

Verify NTE89 Tests using Keysight BenchVue software for E36313A power supply

Connect power supply channel 2 positive terminal to the base, and the negative terminal to the emitter. Use the same hookup as shown in VBE test (shown above). Create a simple script looping CH2 current from 1 mA to 30 mA while measuring CH2 voltage.

Verify NTE89 Tests using Keysight BenchVue software for E36313A power supply.

Upper plot shows current steps across NTE89 base-emitter junction. Lower plot shows measured voltage across NTE89 base-emitter junction. Circled results show the VBE test value at 17 mA, same as test presented above (591 mV). While the first data point on far left shows the same test result a 1 mA as tested for this device using the DMM’s Diode Test Mode (484 mV).

TO-105 / TO-106 Silicon Transistors

2N3638 TO-105 PNP Silicon Transistor

Click image to view PDF datasheet for silicon PNP 2N3638 transistor.

The 2N3638 PNP transistor is designed for small signal, general purpose switching applications.

Test 2N3638 VBE forward biased voltage drop

Probe base (negative lead) to the emitter (positive lead) using DMM’s diode mode.

Test PNP 2N3638 VBE forward biased voltage drop.
Fluke 289 DMM diode mode result.

VBE test result (0.6977 V) in the .5 to 1 VDC range indicates transistor made of silicon.

Test 2N3638 transistor go/no-go gain

Short collector to base using the same probe setup as above for measuring VBE.

Test PNP 2N3638 transistor go/no-go gain.
Fluke 289 DMM diode mode result.

DMM reading will be noticeably lower (0.6444 V) than VBE test result (0.6977 V) above.

Test 2N3638 VCB forward biased voltage drop

Probe base (negative lead) to the collector (positive lead) using DMM’s diode mode.

Test PNP 2N3638 VCB forward biased voltage drop.
Fluke 289 DMM diode mode result.

VCB test result should be slightly lower (0.6919 V) than VBE value (0.6977 V). The lower reading verifies probes are on base and collector. This part has increased readings over time so care must be taken to measure VBE and VBC with the same amount of “on” time.

Test 2N3638 VEC for leakage

Probe emitter (positive lead) to the collector (negative lead) using DMM’s diode mode.

Test PNP 2N3638 VEC for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL indicating no leakage.

Test 2N3638 VCE for leakage

Probe collector (positive lead) to the emitter (negative lead) using DMM’s diode mode.

Test PNP 2N3638 VCE for leakage.
Fluke 289 DMM diode mode result.

For a good transistor, the DMM reading should be OL no leakage.

Verify 2N3638 DMM Tests using Atlas DCA Pro Semiconductor Analyzer

Results from DCA Pro model DCA75 Test and Ic /Vce Curve Trace for 2N3638.

Click the image to enlarge.
Click the image to enlarge.

References

Hardware

Atlas DCA Pro Semiconductor Analyzer

PCA23 – Peak Component Adapter for SOT-23 SMD Transistors

Fluke 289 True-RMS Data Logging Multimeter with FlukeView forms

Keysight E36313A DC Power Supply

Pomona Electronics – 5143-K-48 – SMD Tweezer

PanaVise Model: 201 Jr. with Model: 239 Speed Control Handle

My lab’s support for SMD devices

Click the image to enlarge.

Function generator, Oscilloscope, Stereo Microscope with Camera, Soldier Station, Hot Air SMD Soldier Station, a Wide Range of Components, Cables, Computer Workstation, Parts Listed Above, and etc…

My lab’s additional tools for SMD soldering

Click the image to enlarge.

Soldier (Various Sizes), Soldier Wick, Flux, Tweezers, and etc…

FAQs

Test a transistor with a multimeter

https://vetco.net/blog/test-a-transistor-with-a-multimeter/2017-05-04-12-25-37-07

Semiconductor device numbering/coding schemes

https://www.electronics-notes.com/articles/electronic_components/transistor/transistor-codes-numbering.php

The K.D. Smith Collection By Ed Sharpe (Many references to the M-1752 junction transistor)

https://www.smecc.org/the_k_d__smith_collection_by_ed_sharpe.htm

Books

All New Electronics Self-Teaching Guide, Third Edition; H. Kybett and E. Boysen; Wiley; 2008

https://www.academia.edu/30599085/All_New_Electronics_Self_Teaching_Guide_Third_Edition

Analog Circuit Design, Art, Science, and Personalities; Edited by Jim Williams; Elsevier; 1991

https://www.elsevier.com/books/the-art-and-science-of-analog-circuit-design/williams/978-0-7506-7062-3

1 Reply to “Test Transistors with Multimeter and Semiconductor Analyzer”

  1. Your work here is amazing, I’m really interested in all your results!

    Thank you so much for putting all that time into the testwork.

    On the subject of the M1752, it looks like the Vceo of the device means that it is starting to breakdown as the Vce is getting bigger. This causes an avalanche and therefore the Vce actually drops even though the voltage across the load and the transistor is increasing.

    I note also the interesting and noisy results with one of the darlingtons (BC517). That’s purely because the gain is so high that it is extremely difficult to control the tiny base currents to obtain a suitable curve. The base current control is getting close to the minimum resolution possible and therefore the graph becomes noisy. Very interesting.

    Thanks once again for your brilliant evaluation.

    If you have any questions at all then don’t hesitate to let me know and I’ll be delighted to assist you and your readers.

    Kind regards from us here in the UK,

    Jeremy Siddons
    Engineer and Managing Director
    Peak Electronic Design Limited
    Atlas House, 2 Kiln Lane,
    Harpur Hill Business Park,
    Buxton, Derbyshire,
    SK17 9JL, UK.

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