Pwm pulse generator 2013-09-03

This is the base design (not a full working drawing with pin-numbering etc) for a simple PWM pulse generator using logic gates in a cheap, readily-available CD4011B or CD4049B IC. The pulse duty cycle is variable from 0% to 100%.

View attachment 75707

Circuit Operation

Inverting gates U1b,U1c plus resistors R4,R6 form a Schmitt trigger with upper and lower threshold voltages determined by the ratio of R4:R6.
C1 charges slowly via R1 and discharges rapidly via R5,D1 under the...

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