Transistor testers are instruments for testing the electrical behavior of
transistor
upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink).
A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch e ...
s and solid-state
diode
A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other.
A diode ...
s.
Types of tester
There are three types of transistor testers each performing a unique operation.
* Quick-check in-circuit checker
* Service type tester
* Laboratory-standard tester
In addition,
curve tracer
A semiconductor curve tracer (also known as a semiconductor parameter analyzer) is a specialised piece of electronic test equipment used to analyze the characteristics of discrete semiconductor devices such as diodes, transistors, and thyristor ...
s are reliable indicators of transistor performance.
Circuit Tester
A circuit tester is used to check whether a transistor which has previously been performing properly in a circuit is still operational. The transistor's ability to "amplify" is taken as a rough index of its performance. This type of tester indicates to a technician whether the transistor is dead or still operative. The advantage of this tester is that the transistor does not have to be removed from the circuit.
Service type transistor testers
These devices usually perform three types of checks:
*Forward-current gain, or beta of transistor.
*Base-to-collector
leakage current
In electronics, leakage is the gradual transfer of electrical energy across a boundary normally viewed as insulating, such as the spontaneous discharge of a charged capacitor, magnetic coupling of a transformer with other components, or flow of cu ...
with emitter open(ico)
*
Short circuit
A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circuit ...
s from collector to emitter and base.
Some service testers include a go/no-go feature, indicating a pass when a certain
hfe is exceeded. These are useful, but fail some functional but low h
fe transistors.
Some also provide a means of identifying transistor elements, if these are unknown. The tester has all these features and can check solid-state devices in and out of circuit.
Transistor h
fe varies fairly widely with Ic, so measurements with the service type tester give readings that can differ quite a bit from the h
fe in the transistor's real life application. Hence these testers are useful, but can't be regarded as giving accurate real-life h
fe values.
Laboratory-standard transistor tester or Analyser
This type of tester is used for measuring transistor parameters dynamically under various operating conditions. The readings they give are absolute. Among the important characteristics measured are:
*I
cbo collector current with emitter open (Common base)
*ac beta (Common emitter)
*R
in (Input resistance)
Transistor testers have the necessary controls and switches for making the proper voltage, current and signal settings. A meter with a calibrated "good" and "bad" scale is on the front.
In addition, these transistor testers are designed to check the solid-state diodes. There are also testers for checking high transistor and
rectifier
A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The reverse operation (converting DC to AC) is performed by an Power ...
s.
See also
*
Load pull
Load-pull is the colloquial term applied to the process of systematically varying the impedance presented to a device under test (DUT), most often a transistor, to assess its performance and the associated conditions to deliver that performance in ...
, a colloquial term applied to the process of systematically varying the impedance presented to a device under test
References
{{Electrical and electronic measuring equipment
Transistors
Electronic test equipment