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peak to peak measurement for 1.5 - 2.5 MHz

orhan
Prodigy 50 points

Hi,

I need to detect the peak to peak amplitude of a sine wave with a frequency between 1.5 and 2.5 MHz.

I do not want to use logarithmic amplifiers or RMS to DC converters since the change in my input is quite small (10 to 30% of initial) and those IC's give their outputs in a logarithmic scale. Hence, I would need a very high resolution ADC to detect the changes in the amplitude of the input. 

I thought of using a peak detector with a fast response op-amp. However I would need to discharge the output capacitor which holds the peak value and let it to be charged again with the new peak in order to detect the changes in the peak to peak amplitude of the input signal. I can add a triggering circuit, so the output capacitor would be periodically discharged and be ready for the new peak. But this would lead to glitches in the output that is going to be fed to the ADC and recharging of the capacitor will take some time and my lead to wrong (low) measurement.

Any ideas?

Best regards

  • 0
    Guru 21975 points

    Orhan,

    Often a peak detector uses a resistor or current source to slowly discharge the voltage from acquisition of a peak. Your description sounds as if you are expecting sudden changes in amplitude. Can you explain the speed at which the amplitude can change? Are you expecting to accurately capture amplitude changes that could occur from one peak to the next?

    Regards, Bruce

  • 0 in reply to Bruce Trump
    Prodigy 50 points

    Bruce,

    In fact, I would like to detect voltage drops that typically last for 3 - 10 ms. For 2MHz signal, this would result is 6000 - 20000 cycles. As it turns out playing with sampling capacitor and discharging resistor values would be ok for us.

    Thank you.