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  1. #1
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    pwm circuit schematic

    Dear all:

    I would like to design a pulse width modulation circuit so that my circuit
    will have the different duty cycle ( 50%-50%, 40%-60%, 30%-70%).
    But I don't want to use the dividers to implement it, because it will decrease my output frequency. Anyone has other suggestion?

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    cmos pwm comparator

    did you design a IC PWM or use IC to realise?



    •   Alt4th November 2004, 10:19

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    how to design a pwm

    First of all you need a clock circuit which you can build using to 2 CMOS NAND gates ar 555. Secondly, you need a circuit that will be trigged by this clock and will have ability of changing width of pulses. This can be realised with CMOS CD4528 but instead of connecting only resistor in its RC tank you will connect this resistor through C-MOS switch (eg CD4066). You can use as many switches with different resistors as you wish. Each combination will give you different pulse width.
    Alternatively you can use P-MOSFET transistor as variable resistor or digital potentiometers IC (eg Dallas DS1804-50, 50k, 100 steps) to control the value of R.
    There are thousands way of doing this, it is just the matter of your imagination....

    Other thing is how would you like to control the width of pulses?


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    •   Alt5th November 2004, 00:55

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    comparator cmos circuit

    use 555 to generate slope,a high gain opamp as error amp.& power mos as the output stage.


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    •   Alt5th November 2004, 05:07

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    cmos pwm circuit design

    PWM circuit you can make with simple CMOS comparator that compare from one side sinewave voltage and other side is triangular voltage.



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    pwm cmos circuit

    Try TL494



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    pwm with cd4528

    anyone has the PWM schematic or reference manual ?



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    pwm circuit

    this is a good paper



  9. #9
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    Re: How to design a PWM circuit in CMOS circuit?

    Are you talking about duty cycle corrector or PWM? From your statement, I think is duty cycle corrector.

    PWM is including ramp generator, comparator etc.
    Duty cycle corrector is capacitor plus some other ckt.



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