PNP

1. electronics A type of bipolar transistor consisting of

a layer of N-doped semiconductor (the "base") between two

P-doped layers (the "collector" and "emitter"). PNP

transistors are commonly operated with the emitter at ground

and the collector at a negative voltage.

In the 1960s, the germanium PNP transistor was the cheapest

and best for use at ordinary temperatures. The leakagecurrent from collector to base in this type of device is

larger than for the silicon transistor, and also varies more

with temperature. The effect of these deficiencies can be

lessened by proper biasing and feedback, which can make the

circuit both serviceable and reliable. Neither germanium nor

PNP transistors are as common today.

The voltages used on a PNP transistor are inverted when

compared with vacuum tubes. Further, the behaviour of

vacuum tubes is usually described in terms of voltages

whereas transistors are better described in terms of

current.

2. architecture plug and play.

(1997-05-05)