Hit to the point !I don't think that a single 555 can ever generate linear PWM. The transfer characteristic will be more or less exponentially and never achieve 100% modulation depth.
Hi all
Hit to the point !
555 is not good to create SPWM ! it can be used to generate the square wave and then taking an integral and then comparing the signal with that and then a good linear SPWM which is so trustful !
555 is such a non linear device !
Best Wishes
Goldsmith
O.k., a LM555 pulse width modulator will be fairly linear over a control voltage range of about 1.5 to 10V with 12V supply voltage. You might experience additional non-linerarity from incorrect operation of bootstrap driver (bootstrap capacitor too small).
There are ways to get a 555 to act as a PWM modulator (using some external components), but simply modulating the CV pin is a very poor way to do it. Besides the severe nonlinearity in D, you'll also be modulating frequency quite a bit.
A more straightforward way to make a linear PWM modulator is to create a nice linear ramp waveform using an op amp oscillator, then feeding that and your audio signal to a comparator. Look at the top of page 9 of this document: **broken link removed**
Did you check bootstrap operation at high duty cycle?
Anyway, it was just a guess. To determine if the NE555 is still in linear range, you have to check the absolute CV pin level in relation to VCC. Did you?
Ordinary op amps and comparators should be able to do 10KHz no problem. A TL082 and a LM339 will do it no problem, and those parts should be available anywhere.i know this method but the only thing that made me to choose the NE555 time is because in my country i didn't find a good comparator that could compare a triangular wave of 10KHZ with a sine wave of 50HZ in fact when i did the design on simulation i used this method to generate the PWM signal .
Ordinary op amps and comparators should be able to do 10KHz no problem. A TL082 and a LM339 will do it no problem, and those parts should be available anywhere.
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