If the transistor passes all the tests then, it is functional and all the junctions are in healthy condition. Again, the meter should read open circuit. ![]() The leads may be labeled B, E, and C or the orientation within the circuit may reveal which. The meter should read open circuit in this case.Īlso, connect the positive probe of the meter to emitter and the negative probe to the collector. Identify the base, collector, and emitter leads on a transistor. Now, connect the negative probe of the meter to the emitter and the positive probe to the collector. The variation of collector current (I C) with Collector-Base voltage (V CB ), keeping the emitter current (I E) constant. of two diode junctions, the base-emitter junction and the base-collector junction. The transistor characteristic under Common Base configuration is as follows: The variation of emitter current (I E) with Base-Emitter voltage (V BE ), keeping Collector Base voltage (V CB) constant. Again, the multimeter should read open circuit. BC547 is a NPN transistor hence the collector and emitter will be left open (Reverse biased) when the base pin is held at ground and will be closed (Forward biased) when a signal is provided to base pin. Section 7.3 Testing Transistors The Two Diode Model for BJTs. This time, the multimeter should read open circuit.Ĭonnect the positive probe of multimeter to the collector terminal. Now, connect the negative or common probe of multimeter to the base terminal of the transistor.Ĭonnect the positive probe of multimeter to the emitter terminal. Again, the multimeter should give some reading. The multimeter should give some reading.Ĭonnect the negative or common probe (Black coloured) of multimeter to the collector terminal. Set the digital multimeter to Diode or Continuity range.Ĭonnect the Positive probe (Red coloured) of multimeter to the base terminal of the transistor.Ĭonnect the negative or common probe (Black coloured) of multimeter to the emitter terminal. In the same manner, we can test a PNP transistor too. We can test an NPN transistor by testing the junction's continuity in the forward bias and reverse bias mode. When the reverse bias applied to the junction, it behaves as an open circuit. The test of the transistor is based on the principle of pn-junction biasing, i.e., when a forward bias is applied to the pn-junction (by connecting positive terminal to the p-region and negative terminal to the n-region), the junction allows current to through it. By examining both the junctions (Emitter-Base junction and Collector-Base junction) with the help of a digital multimeter, we can comment on the functionality of the transistor. H fe is measured and the transistor is reported good if this metric exceeds a specific level. Basically a transistor is nothing but two pn-junctions connected back to back. This instrument performs three measurements for bipolar transistors: forward current (beta), base-to-collector leakage current with open-emitter and short-circuit from collector to emitter and base.
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