Bipolar RF Transistors

RF bipolar transistors consist of an N-type or P-type layer sandwiched between two layers of the opposite type. They are designed to handle high-power radio frequency (RF) signals in devices such as stereo amplifiers, radio transmitters, and television monitors. Like other semiconductor devices, RF bipolar transistors are made of materials such as silicon (Si) or germanium (Ge) and doped with impurities to induce changes in electrical properties. The junctions between the semiconductor sections cause a weak input to be amplified. Varying the current between the base and the emitter varies the current flow between the emitter and the collector. In normal operation, the emitter-base junction is forward-biased and the base-collector junction is reverse-biased. In the linear region, the collector-emitter current is approximately proportional to the base current, but many times larger. In the cut-off region, the base-emitter voltage is too small for any significant amount of current to flow.