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pulse burst averaging circuit

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cwaitang

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I am looking for circuit for detecting avaerage of pulse bursts as small as 50mV, not the rms value of signal almost zero.

The signal frequency is 15-33khz with 50% duty cycle which translates to 15 to 30usec pulse width, in bursts of 4 to 8 cycles every 250ms. An internal ADC within a MCU is used to do the sampling. It has acquistion delay of 10s of usec. This is typical conversion time of most common inexpensive ADCs.

Hence I need averaging circuit which produces an output corresponding to the average of pulse amplitudes within single burst (the larger the pulses, the larger the output) and can hold it for ADC conversion.

Anyone can help please provide pointers. Thanks!

I came across the following circuit. Can this circuit work to above purpose?

1)What happens when rail to rail limitation of op amp sets in? How to correct for this?
2)Does pulse amplitude need greater than Vbe for pnp transistor to turn on? if so, any way to go around this to make circuit work for input amplitude low as 50mV?
 

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MikeMl

Well-Known Member
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All I see is an amplifier, a level shifter, and a peak detector. There is no discharge path for the capacitor, so what resets it? It captures peaks; not averages.

I think you want a "precision rectifier", followed by a "low-pass filter" with the cutoff frequency set well below the sampling interval. You might have to take a series of ADC samples, and then use software to select the highest local sample...
 
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