Long time delay circuit formed by the power MOSFET

Published:2011/7/26 10:06:00 Author:Nancy | Keyword: Long time delay, power MOSFET | From:SeekIC

Figure 1 is a long time delay circuit formed by the power MOSFET. The grid input impedance of the power MOSFET is very high, so it is easy to choose the resistor and capacitor with large grid time constant. When the gate opens, the gate control switch S1 conducts, the base of VT1 is low level and in the conduction state, so the grid of the power MOSFET (VT2) is high level and conducts, the indoor light H is lit up. When the gate is closed, the gate control switch S1 disconnects, the base of VT1 is high level and cut off. However, the time constant formed by the R1 and C1 make VT2 conduct for lOs, which keeping the grid voltage of VT2 higher than threshold voltage. With the discharge of C1, the grid voltage of VT2 reduces and cuts off, the indoor light H burns out.



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