i need to detect the peak to peak value of a sine wave. i have some circuits, but the problem is the required bandwidth is 10Hz-200KHz and none has worked out properly. NEED HELP URGENTLY.....
ya, its enough to find only the positive peak value and get it multiplied with 2.
my main problem is, the circuits i tried is having capacitors to hold the peak value. but at high frequencies its not getting enough time to charge completely so the voltage across the capacitor is not the actual peak value. how much ever time i give, its not getting charged completely at high frequencies. i think this capacitor need to be eliminated. any idea how to do it?
200 kHz isn't actually a very high frequency. Classical peak detector circuits can handle it with sufficient fast OPs. In any case,
you have to be aware of non-ideal circuit properties, so the design has to start with - besides operation frequency - a specification
of relative and absolute error and acceptable droop.
I just tried with my circuit but used faster op amp. also switched the capacitor 2 or 3 times while going from low to high frequency. now things are working perfectly...
The problem with the simpler circuits is the output sits at the negative rail so when a pulse comes along it has a long way to get to the peak value. The dual opamp version I posted holds the output one diode volts drop below the input so the output hasn't got as far to go when a peak comes along, so the slew rate requirement is less.