OPA177: Peak Detector Circuit Issue

Bruno D.

Prodigy 130 points

Part Number: OPA177

Hello All,

I'm trying to use the OPA177GS as a peak detector, as shown in the circuit.

My issue is that, theoretically the output should be able to maintain the peak voltage.

Does the op-amp has somekind of internall resistance in parallel with the RC values that reduces the R value ?

Thank you for the help.

over 3 years ago

0 Raymond Zhang1 over 3 years ago

TI__Guru 51561 points

Hi Bruno,

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The op amp's output is relative low impedance. Please send us the circuit and I will simulate it for you.

Best,

Raymond

0 Bruno D. over 3 years ago

Prodigy 130 points

Hello,

The circuit is bellow :

Thank you

0 Raymond Zhang1 over 3 years ago in reply to Bruno D.

TI__Guru 51561 points

Hi Bruno,

In order to hold the charge at 100nf a longer period of time, you need to select low leakage diode. Try the following circuit, it may help to prolong the discharge current via diode D1 to the op amp.

Also, you may consider to use low leakage capacitors, such polyprolyene/teflon types, because certain types of capacitors do not hold the charge longer due to leakage.

If you use switch to replace the 68kOhm resistor, then you can remove the resistor, since it also discharges the voltage across the capacitor C1.