Bipolar transistor

Bipolar transistor integrated circuits were the main active devices of a generation of mainframe and minicomputers, but computer systems now use complementary metal–oxide–semiconductor (CMOS) integrated circuits relying on the field-effect transistor (FET). Bipolar transistors are still used for amplification of signals, switching, and in mixed-signal integrated circuits using BiCMOS. Specialized types are used for high voltage and high current switches, or for radio-frequency (RF) amplifiers.