# Transistor material, tube type and polarity judgment

Source: Internet
Author: User

If the measured amplification circuit of several transistors three pin to ground point U1.U2.U3 are the following values, try to determine whether they are silicon tube or germanium tube, is NPN or PnP tube. and determine three electrodes of 1. u1=2.5v. u2=6v. u3=1.8v 2. u1=-6v. U2=-3v. u3=-2.8v I would like to draw up a detailed answer procedure.

A: (authoritative release, to find the law)

1, u1=2.5v. u2=6v. u3=1.8v, it is known that the base is the corresponding U1, the emitter is the corresponding U3 (because the silicon tube is a potential difference is 0.7V), the Collector is the corresponding U2, because the highest potential is the collector, so is the PNP silicon transistor. 2, u1=-6v. U2=-3v. u3=-2.8v, it is known that the base is the corresponding U2, the emitter is the corresponding U3 (because the germanium tube be potential difference is 0.2V to 0.3V), the Collector is the corresponding U1, so it is the NPN germanium transistor.

Note: First determine the base (electricity in the top), and then determine the emitter (by the Be potential difference is about 0.7V-silicon tube, 0.2 to 0.3V or so-germanium tube), the remaining is the collector. Last look: If the collector potential is the highest, the corresponding is the NPN tube, if the emitter potential is the highest, corresponding to the PNP tube.

Summarize:

(1) Determine the tube material:

In the amplified state of the transistor, the voltage between the base and the emitter is basically equal to the diode's forward voltage, the general silicon diode on the 0.6 to 0.7V, the germanium diode conduction voltage around 0.2V.

(2) Determine which type of tube is part of:

(2) Known pipe type, determine polarity:

Transistor in the normal working state,

In the case of an NPN tube, the uc>ub>ue must be guaranteed, and the ub-ue=0.7v (the transmit junction is positive, set the electrical junction inverse).

In the case of PNP tubes, the UE>UB>UC must be guaranteed and ue-ub=0.7v-

Note: Current flows from high EMF to low EMF.

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