Simple pulse width modulation circuit

Published:2011/8/23 22:27:00 Author: | Keyword: Simple, pulse width, modulation | From:SeekIC

The simple pulse width modulation circuit is as shown in the figure. It uses the operational amplifier to form the multivibrator, so we can get the positive and negative symmetrical oscillation output signal with the duty ratio of 50%. If we change the threshold voltage from external, we can realize the pulse width modulation. If this circuit is not connected with the resistor R1, the oscillation frequency f0 is decided by the cycle of the hysteresis voltage, f0=1/2R4C1ln(1+(2R2/R3)). If [1+(2R2/R3)]=2.718, the f0=l/(2R4C1), so we can change the duty ratio by using the external voltage to move the ±UTH through R1.



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