3/27/2023 0 Comments Transistor tester![]() ![]() An excessive I cbo indicates a faulty transistor. This is reverse current from the collector to the base, with the emitter open, denoted I cbo. Other causes of this condition are overheating, or other types of damage. Excessive leakage generally occurs when the conductor surface is contaminated. Direct Measurement of Collector – Leakage Current:Ĭollector-leakage current is a function of the temperature and resistivity of the material of the transistor. If the reading in the short position is less than the maximum allowable amount indicated on the chart, the next test for reverse current I cbo, is set up. In that case, no further tests are performed on that transistor, thus avoiding possible damage to the meter circuit. If there is a breakdown (usually from collector to emitter), the indicating meter tends to read full scale deflection. 10.18 (b) shows an arrangement for an NPN transistor. Figure 10.18(a) shows an arrangement for a PNP transistor and Fig. 10.18, the emitter and base terminals of the Transistor under test are tied together and a reverse voltage of 4.5 V is applied between the collector and the two leads that are connected together. In the arrangement for the short-circuit test given in Fig. Short – Circuit Test for C – E Breakdown: Four Terminal Parameter Test (Hybrid Parameters)ġ.Direct Measurement of Collector-Leakage Current.It is an comparatively difficult measurement because of the small currents involved (in μA), and because of its extreme temperature sensitivity.Ī typical service type transistor and diode tester examines transistors for the following characteristics. The latter measurement of C to B reverse current is generally regarded as most significant to test for the ageing of a transistor. A value for collector to base leakage current, with emitter open I cbo.A value for the forward gain in the common emitter configuration (h FE for ac gain or h FE for dc gain), that is β gain. ![]()
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