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Is there something wrong with this Precision half-wave Rectifier circuit?

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It would be useful if you upload the image here- one link doesn't work - I get a 3MB blank screen and the other is so slow I gave up.

Keith.
 


I simulate with it but the result is wrong.

Problem is on output point. Do it like here....
Prec_Rect_HW_.jpg


Precision rectifier - Wikipedia, the free encyclopedia
 
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I want to design a Non-inverting Precision half-wave Rectifier. This is my design. And I simulate with it but the result is wrong.

Simply remove D2 (resp. D3b) from your design, if you want a half-wave rectifier.
 

It does work right when input is positive but not when input is negative. Right?
You can use the inverting configuration plus an inverting stage.
Do you use a split supply, right?
Regards

Z
 

for positive half the D2 is short circuit while d1 is conducting u r getting the output
but in negative half D2 is shorting the feedback loop
whats the purpose of R3???
its just limting the current???
 


Hi wchzym,

in your second circuit, if the right terminal of R9b (or directly the non-inverting input) were at ground and the input voltage were applied to the right terminal of R8b (instead of grounding it) this would be a standard precision rectifier in inverting configuration.
Changing the role of ithe two inputs (right terminals of R9b and R8b) does not transform inverting in non-inverting without any other change.
In the first case, you have a virtual ground at the inverting input if the OA. In the second, you have a "virtual Uin" at the non-inverting input. As a consequence, you have non-null output from the circuit when input is negative.
I suggest: using the principle of virtual ground, analyse whay happens in the standard (inverting) configuration. Then analyse your circuit.
You will see why in the first circuit you get gain=2 for positive halfwaves and 1 for the negative ones. (In the first circuit, output is at the cathode of D1.)
Regards

Z
 

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