The fixed cycle pulse generator circuit with the adjustable duty ratio

Published:2011/5/25 6:15:00 Author:Christina | Keyword: fixed cycle, pulse generator, adjustable, duty ratio | From:SeekIC

As the figure shows, the astable multivibrator is composed of the 555, VT1, VT2, R1, R2, RP1 and C1. In this figure, the capacitor C1 has the independent charging and discharging circuit, when you adjust RP1, you can change the charging and discharging time constants, but can not change the oscillation frequency. Before C1 is charged to the 2/3VDD threshold electrical level, pin-3 has the high electrical level, that means during the time of t1, VT2 conducts, VT1 fully conducts, so VT1 has the small impedance. By adjusting RP1, you can change the duty ratio between 2% to 98%, the period can not be changed.



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