| 摘要 |
PURPOSE: A hysteresis circuit using band gap reference circuit is provided to supply stable DC voltage independent of thermal changes. CONSTITUTION: A hysteresis circuit using band gap reference circuit includes following steps. As constant voltage(Vcc) increases from 0, the base voltage(VB) and the emitter voltage(VE) also increase and the first and second constant current(I1,I2) run in the first and second transistors(Q1,Q2). If the level of the constant voltage(Vcc) is low, the second transistor(Q2) goes into a saturation mode with the base current since the required second constant current(I2) is not supplied and the third transistor(Q3) is turned off. If the constant voltage(Vcc) keeps increasing until I1 = I2, the second transistor(Q2) moves from saturation mode to active mode, when the third transistor(Q3) is turned on and the load operates. The turning off procedure is opposite to the turning on procedure.
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