Quantcast Testing Transistors with an Ohmmeter

Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Custom Search
 
  
 
2-34 Transistor testers are nothing more than the solid-state equivalent of electron-tube testers (although they do not operate on the same principle). With most transistor testers, it is possible to test the transistor in or out of the circuit. There are four basic tests required for transistors in practical troubleshooting: gain, leakage, breakdown, and switching time. For maintenance and repair, however, a check of two or three parameters is usually sufficient to determine whether a transistor needs to be replaced. Since it is impractical to cover all the different types of transistor testers and since each tester comes with its own operator's manual, we will move on to something you will use more frequently for testing transistors-the ohmmeter. Testing Transistors with an Ohmmeter Two tests that can be done with an ohmmeter are gain, and junction resistance. Tests of a transistor's junction resistance will reveal leakage, shorts, and opens. TRANSISTOR GAIN TEST.—A basic transistor gain test can be made using an ohmmeter and a simple test circuit. The test circuit can be made with just a couple of resistors and a switch, as shown in figure 2-18. The principle behind the test lies in the fact that little or no current will flow in a transistor between emitter and collector until the emitter-base junction is forward biased. The only precaution you should observe is with the ohmmeter. Any internal battery may be used in the meter provided that it does not exceed the maximum collector-emitter breakdown voltage. Figure 2-18.—Testing a transistor's gain with an ohmmeter. With the switch in figure 2-18 in the open position as shown, no voltage is applied to the PNP transistor's base, and the emitter-base junction is not forward biased. Therefore, the ohmmeter should read a high resistance, as indicated on the meter. When the switch is closed, the emitter-base circuit is forward biased by the voltage across R1 and R2. Current now flows in the emitter-collector circuit, which causes a lower resistance reading on the ohmmeter. A 10-to-1 resistance ratio in this test between meter readings indicates a normal gain for an audio-frequency transistor. To test an NPN transistor using this circuit, simply reverse the ohmmeter leads and carry out the procedure described earlier.


Electrical News
Moog Theremini Melds Analog & Digital
Robert Moog, the inventor of the voltage-controlled oscillator that enabled...
eetimes.com
Power Week: Thermoelectric Energy Harvesting's Bright Future
This week, the future of sub-watt thermoelectric energy harvesting as...
eetimes.com
Energy Harvesting Chip Demonstrated
Imec and Omron have collaborated on a tiny 5x6 cm...
eetimes.com
EEVblog #644 – How To Design Front Panels On Extruded Enclosures – µSupply Part 14
Dave shows some techniques on how to build and mount...
eevblog.com
Silicon Photonics Acquires Key Subsystems
Silicon photonics will someday replace the expensive gallium arsenide photonics...
eetimes.com
Apollo 11 Inspired Generations of Innovators
Neil and Buzz were on the moon. Orbiting above, there...
eetimes.com
Smartwatches Suck, Says Pebble Backer
There are only two significant platforms in the smartwatch arena...
eetimes.com
Future Engineers: Don't 'Trip Up' on Your College Road Trip
A future engineering student gives his advice on making the...
eetimes.com
Future Engineers: Don't 'Trip Up' on Your College Road Trip
A future engineering student gives his advice on making the...
eetimes.com
DARPA's Chip Office Reboots to Tackle Cost & Complexity
DARPA's Microelectronics Technology Office, the source of much chip innovation...
eetimes.com
Imagination Positions Itself for 802.11ah for the Internet of Things
Imagination Technologies has developed a low-power configurable radio architecture for...
eetimes.com
Mentor Launches Xpedition PCB Data Management Solution
The new Xpedition data management solution will ensure flow-wide PCB...
eetimes.com
Juggling a Cornucopia of Projects
Max is juggling so many hobby projects that it's no...
eetimes.com
Develop & Share Open-Source Hardware Projects
Matlab and Simulink are finding use in projects that don't...
eetimes.com
Android Open-Source for ARMv8-A Starts 64-Bit Avalanche
Mobile devices will need a big boost in processing power...
eetimes.com
Find an Entrepreneurial Mentor
As Luke had his Yoda, so does a startup CEO...
eetimes.com
Are We Ready to Give Up Driving?
In a Strategy Analytics survey, 40% of Americans said they...
eetimes.com
Broadcom Cuts 2,500 jobs
Broadcom announced plans to cut 2,500 jobs, 20% of its...
eetimes.com
AMS, Dialog Merger Talks Fail
Talks over a possible merger of mixed-signal chip companies AMS...
eetimes.com
The Risks & Rewards of Early Tapeout
Verification remains a key issue in system-on-chip development. The time...
eetimes.com
 


Privacy Statement - Copyright Information. - Contact Us

comments powered by Disqus

Integrated Publishing, Inc.
9438 US Hwy 19N #311 Port Richey, FL 34668

Phone For Parts Inquiries: (727) 755-3260
Google +