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Accurate reading of an analog pulse peak or valley

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djnik1362

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hi everyone

I need to read peak or valley of an analog pulse with 400ns minimum pulse width.
When there is pulse the signal value can be from 0 to 1.8V and when there is no pulse the signal
can be any voltages from 0 to 1.8V . So there is peak or valley in different situations.
There is a digital trigger signal that shows me there is pulse on the analog signal.

I guess i can use a MOSFET (such 2N7002) to sample analog signal at pulse duration
but i don't know practical issues . I need a reference circuit or chip if you suggest any.
I am using AVR Xmega micro controller from Atmel for reading analog sample and pulse PRF
is 1000 at maximum (1000 pulses in one second). The resolution of reading must be lesser than 10mv.

Thanks for your support.
 

Regarding sample-and-hold chips, I would simply assume that ICs like AD783 with sufficient speed aren't available in your country. Sorry for that.

Sample and hold circuits with OPs and separate analog switches are shown in many OP application circuit collections. I would consider 74HC4066 or other dedicated CMOS analog switches. Compared to 2N7002 they have much lower charge injection, which is a prerequisite to achieve the intended 10 mV accuracy. A MOSFET with substrate diode like 2N7002 is also not suited to process bipolar (positive and negative) pulses. You have to refer to MOSFETs with separate substrate terminal, there are very few types available.
 
Regarding sample-and-hold chips, I would simply assume that ICs like AD783 with sufficient speed aren't available in your country. Sorry for that.

Sample and hold circuits with OPs and separate analog switches are shown in many OP application circuit collections. I would consider 74HC4066 or other dedicated CMOS analog switches. Compared to 2N7002 they have much lower charge injection, which is a prerequisite to achieve the intended 10 mV accuracy. A MOSFET with substrate diode like 2N7002 is also not suited to process bipolar (positive and negative) pulses. You have to refer to MOSFETs with separate substrate terminal, there are very few types available.

Thanks . I think AD783 is a good choice. My signal is uni-polar and as i said it is between 0 and 1.8V.
 

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