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
MEMS-Based Laser Headlights Adapt to Speed
On the basis of its laser spot high-beam headlight, Audi...
eetimes.com
XeThru Technology is One to Watch
Novelda, under the leadership of CEO Alf-Egil Bogen, is seeking...
eetimes.com
China Advantage Wanes for OEMs
Once the clear winner for OEMs in terms of low-cost...
eetimes.com
Engineering Congress
Congress needs an engineering mindset....
eetimes.com
Vest Uses Haptics for Speech by Feel
The Versatile Extra-Sensory Transducer (VEST) under development at Rice University...
eetimes.com
Lattice Deal: Harbinger of FPGA & ASSP Union
Lattice CEO, after its acquisition of Silicon Image in March,...
eetimes.com
IoT and Services are Transforming Manufacturing
Manufacturing will evolve in the IoT era from simply producing...
eetimes.com
Mega-Cool Breadboarding Multi-Tool Kickstarter Project
Even though Max considers himself to be something of a...
eetimes.com
Effective Code Coverage Comes to Multicore Software
New code coverage tool gives greater visibility into software running...
eetimes.com
Introducing FPGAs to MCU Gurus
Hardware guys and gals know how all this stuff works...
eetimes.com
IBM Tackles Phase-Change Memory Drift, Resistance
Researchers demonstrate that reliable 2 bits-per-cell storage and subsequent data...
eetimes.com
Engineer Building Google for Chips
An engineer-turned-entrepreneur aims to develop a Google for semiconductors, making...
eetimes.com
Sensors, Auto Power Drive ST Revenues
STMicroelectronics revenue, totaling $1.71 billion in Q1, came from power...
eetimes.com
Friday Quiz: Capacitors
Capacitors are fundamental electric-circuit components, but there's more to using...
eetimes.com
Lead Acid Battery Balancer
Active balancing of series connected battery stacks exists for many...
eetimes.com
Chip Incubator Debuts Startups
Semiconductor incubator Silicon Catalyst officially announced its first startups working...
eetimes.com
60V LED Driver with Internal 4A Switch for Automotive Lighting
LED lighting is an important feature in today's and future...
eetimes.com
H-1B Visas Tougher To Come By In 2015
Demand for new H-1B visas far outpaces supply in the...
eetimes.com
NXP CEO on China, Apple Pay, IoT & V2V
In unveiling its Q1 earnings, NXP CEO talks about the...
eetimes.com
Google Fi Bets On Cheap Wireless
Google's latest venture into wireless phone service will give the...
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 +