Rail to Rail High Bandwidth and High slew rate opamp

Tony Stewart · Jan 18, 2016

MrAl said:
Tony:
I think the output cap voltage will 'pump' up to the input to some degree because there is a rectifier so it is not 'just' about the voltage divider ratio of cap values, however some calibration would be required because there will still be loss in the diode(s). How much loss would have to be compared to the scope measurements and may or may not affect the overall measurement if the input signal is large. The ratio of caps does seem pretty large however, that seems a little too extreme.

Yes with no load it would pump up to twice the input peak level.

Then down to the cap ratio of 2* 1/1000 for an RC decay time that follows the wave frequency

But variable levels in between depending on f and load impedance with a ratio of ~R/(Xc(f)+R)
So the bandwidth of the envelope bandwidth response determines the DC/AC voltage ratio in practical terms for this "peak detector"

This also assumes AC peak >> diode drop.

However, this cct. is unsuitable for accurate burst or pulse signal detection.

MrAl · Jan 18, 2016

Hi,

Yes, output impedance will have a lot to do with it too. 10Megs wout load much 1 meg a little more, but 10k will load it down to probably almost half the expected normal output. This means calibration with a scope is a necessity.
Yes again, this only works with repetitive signals.

spec · Jan 18, 2016

Akbar Quraishi · Jan 25, 2016

Hey Spec
What Op amp model number you used?

Rail to Rail High Bandwidth and High slew rate opamp

Tony Stewart

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MrAl

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spec

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Akbar Quraishi

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Rail to Rail High Bandwidth and High slew rate opamp

Tony Stewart

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spec

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