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
Friday Quiz: Bipolar Transistors
Remember basic transistor physics? Let's see if you really do....
eetimes.com
9 Top Tech from Electronica 2014
After 50 years, Europe's bellwether conference Electronica shows the state...
eetimes.com
Micron Expands IoT & Auto Memory Products
Micron expanded its offerings for embedded applications and the connected...
eetimes.com
Moore's Law Competitor Wins $150K Elevator Pitch Prize
Quilt packaging wins $150,000 prize for best elevator pitch explaining...
eetimes.com
Nexus 6 Vs. iPhone 6 Plus: Phablet Deathmatch
There's never been a better time to buy a big-screened...
eetimes.com
Europe vs. Google
Google may not give much thanks for the gift Europe...
eetimes.com
Stephen Hawking: How He Speaks & Spells
The technology that helped resurrect the life of Stephen Hawking...
eetimes.com
Sony's 3-Year Plan: Treading Water or Just Sinking?
Sony's three-year outlook for its mobile business "isn't aiming for...
eetimes.com
HMC Spec Update Signals Healthy Adoption
The release of the Hybrid Memory Cube specification 2.0, along...
eetimes.com
Power Week: Si-Based Power Discretes to Continue to Dominate Over Next Decade
Discrete power electronics are predicted to become a $23 billion...
eetimes.com
Book Review: Deadly Odds by Allen Wyler
This is a great read that will have you on...
eetimes.com
Supercapacitors: A New Hero in the Spotlight
Today's supercapacitors are being used to replace rechargeable batteries in...
eetimes.com
EEVblog #687 – EFTPOS PIN Pad Terminal Teardown
What’s inside a smart card pinpad EFTPOS terminal? Dave looks...
eevblog.com
Your Part in the Recovery
Engineers and innovators are central to the slow but ongoing...
eetimes.com
Motor Controllers Offer Improved Noise Immunity
Operating at 5V gives these digital signal controllers enhanced noise...
eetimes.com
NXP to Pick Up Its Missing IoT Link - Bluetooth Low Energy
In pursuit of the Internet of Things market, NXP Semiconductors...
eetimes.com
USB Oscilloscopes Get Beta Drivers for Open-Source Hardware
Pico Technology has released beta versions of drivers for BeagleBoneBlack...
eetimes.com
It's Alive! The 3D Printing of Living Tissues
Within a generation, we likely will not just hear of...
eetimes.com
Curiosity Killed the Cat (Just Call Me Mr. Curiosity)
Max desperately needs a cat deterrent, but how should this...
eetimes.com
Memory Design Articles: Diagnostics, Datacenters & Failures
Here's a roundup of recent design articles that are relevant...
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 +