![]() Heat sinks can be used that carry away extra heat and prevent the base–emitter temperature from rising.Hence, the increasing collector current throttles its source. Negative feedback can be built into the biasing circuit so that increased collector current leads to decreased base current. ![]() There are several approaches to mitigate bipolar transistor thermal runaway. This deleterious positive feedback results in thermal runaway. Depending on the bias point, the power dissipated in the transistor may also increase, which will further increase its temperature and exacerbate the problem. ![]() By the Ebers–Moll model, if the base–emitter voltage V BE is held constant and the temperature rises, the current through the base–emitter junction I B will increase, and thus the collector current I C will also increase. Often, the Q-point is established near the center of the active region of a transistor characteristic to allow similar signal swings in positive and negative directions.įor digital operation, the Q-point is instead chosen so the transistor switches from the "on" (saturation) to the "off" (cutoff) state.Īt constant current, the voltage across the emitter–base junction V BE of a bipolar transistor decreases by 2 mV (silicon) and 1.8 mV (germanium) for each 1 ☌ rise in temperature (reference being 25 ☌).
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