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 leakage current 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.
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