You just need a dual comparator. One comparator (with an open collector output) makes a sawtooth oscillator at a fixed frequency. The C charges slowly via R, then the open collector output discharges C very quickly giving a sawtooth output.You mean the LM393 (dual comparator)? It is good for 36V. Two chips, 40106 and LM393, I didn't spell it out before but that is what I was thinking.
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I can't hear the difference between an f and and s anymore these days anyway. I say "Huh?" and "What?" and "Say again?" a lot, especially if there's background noise.Telephones sound awful, especially cell phones. ALL the high frequency sillibants of speech are gone so it is difficult to understand what is being said.
ee de'ingner' o' 'ele'one' 'ould be 'o'. (Just vowels.)
Translation to wideband audio: The designers of telephones should be shot.
You'll need a delay line so you know when to ramp up the voltage and a supply capable of charging the capacitors rapidly (<10ms), but it definitely could work.As far as keeping Vdd well regulated, why not have the input signal change the duty cycle of a switching supply for the rails, and end up with full Class G (or whatever letter they call it since it isn't a standard yet)? Extremely high efficiency, as you are only switching enough current to reproduce the sound, and aren't holding ±30V rails when listening to quiet music, dynamic headroom would be extreme, as the supply could boost to ±60V for transients.
You would get the same effect from something as simple as employing closed loop feedback at the amp output, which adjusts the PWM so the voltage at the speaker is the same as the input signal....
As far as keeping Vdd well regulated, why not have the input signal change the duty cycle of a switching supply for the rails, and end up with full Class G (or whatever letter they call it since it isn't a standard yet)? Extremely high efficiency, as you are only switching enough current to reproduce the sound, and aren't holding ±30V rails when listening to quiet music, dynamic headroom would be extreme, as the supply could boost to ±60V for transients.
The best way I can think of doing this is to use a regulated supply for the audio but power the PWM oscillator off the unregulated supply. A 555 timer will follow the change in supply voltage. It wouldn't eliminate all noise, though.You would get the same effect from something as simple as employing closed loop feedback at the amp output, which adjusts the PWM so the voltage at the speaker is the same as the input signal.
So the PWM would self-adjust and compensate for any PSU ripple, PSU sag etc (as it does in an analogue amp). That's how I would do it, but Bill said this was for a minimum parts count type "educational" design?
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