pwm - 4QD-TEC: Electronics Circuits Reference Archive Pulse...

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4QD-TEC: Electronics Circuits Reference Archive Pulse Width Modulators Generating a PWM waveform is extremely simple! This page demonstrates a circuits for doing this and discusses some of the considerations. All of the circuits are d.c. input to p.w.m. out. Op-Amp/Comparator The first example uses the standard op-amp oscillator circuit to generate a triangular waveform which is level-shifted and fed to a comparator (e.g. LM339) to give the PWM waveform. Most people will want to use two comparators rather than one op- amp and one comparator so that is what we show here. The triangle wave oscillator is formed around Cp1. Consider the initial state with C1 uncharged. The comparator's - input will be low, so the comparator's output will be high (off) and C1 will charge (from the comparator's output) via R2 and R1. The comparator's +ve input will be biased to about 2/3 of the supply voltage (Vcc) since R5 is, in effect, in parallel with R3. So, when C1 charges above 2/3 of the Vcc, the comparator will turn on, its output
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This note was uploaded on 05/04/2009 for the course COMMUNICAT ee526 taught by Professor Mousamousa during the Spring '09 term at Alexandria University.

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pwm - 4QD-TEC: Electronics Circuits Reference Archive Pulse...

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