Here's the LTspice simulation of a simplified version of the no-diode precision rectifier.
I used a different op amp but it should also work with the Microchip device.

View attachment 115638

Hi crutschow, I have used your version of the no-diode precision rectifier but I did not manage to get the signal rectified. It was still the same 500kHz sine wave that I have input. Is there a problem with my breadboard? I have attached my set-up as shown below.

 

Does it work at a lower frequency?

 

if you need a full wave rectifier, diodes are the simplest solutions. (voltage) opamps aren't good for high frequency applications.

If you have to go down that path, look for current feedback opamps. Those things go into the Mhz easily.

 

Does it work at a lower frequency?

I think crutschow is onto the problem.

This circuit depends on the output of the op-amp saturating. Once the op-amp saturates it can take a _very_ long time to recover.

I think a more conventional precision rectifier circuit will work better. These circuits have an additional diode to keep the op-amp from saturating.

By the way, I don't see any bypass caps in your circuit. See my notes in your other thread.
http://forum.allaboutcircuits.com/threads/wien-bridge-of-500khz-but-only-able-to-get-335khz.129478/

 

You're not using an negative power supply are you? crutschow's circuit only uses V+ and Ground.

 

Hi everyone, thanks for the help. So sorry that I was not around for the past weeks as I was having my finals. Now, I'm back to continue on the project!

 

Does it work at a lower frequency?

Hi crutschow! It does work in low frequencies as shown below but does the measurement of the frequency on the oscilloscope has to be the same as my function generator? As the measurement on the oscilloscope is 2kHz than 1kHz.

If I use 200kHz on the function generator, the oscilloscope measurement is like this.

This is 500kHz on the function generator.

 

I think crutschow is onto the problem.

This circuit depends on the output of the op-amp saturating. Once the op-amp saturates it can take a _very_ long time to recover.

I think a more conventional precision rectifier circuit will work better. These circuits have an additional diode to keep the op-amp from saturating.

By the way, I don't see any bypass caps in your circuit. See my notes in your other thread.
http://forum.allaboutcircuits.com/threads/wien-bridge-of-500khz-but-only-able-to-get-335khz.129478/

Hi RichardO, sorry for asking you again. "A more conventional precision rectifier circuit will work better. These circuits have an additional diode to keep the op-amp from saturating.", may I know which circuit you're mentioning about? Do you have the circuit diagram of it?

Is this the circuit you're referring about?

Thanks in advance!

You're not using an negative power supply are you? crutschow's circuit only uses V+ and Ground.

Thank you DickCappels! I have rectified that error and now is able to get the precision full wave rectifier up and running at 1kHz but not at the 500kHz that my project wants.

 

It's not easy to achieve the clean, high speed precision rectification you want.
Below is the LTspice simulation of a precision rectifier circuit that avoids op amp saturation and appears to work fairly well at 500kHz.
It has the advantage over some other configurations, such as the one in post #28, of requiring only two matched resistors (R1 and R2) for good amplitude match of the two halfs of the rectified wave.
C1 is needed to prevent high frequency oscillations in the waveform. Its value likely will have to be tweaked for the best waveform in the actual circuit.
The circuit will also require careful layout (preferably on a ground plane) and power supply decoupling with 0.1μF ceramic caps at the op amp pins (not shown) for best performance. It likely won't work well on a plug-in breadboard such as shown in post #27.
It uses high speed op amps to achieve the desired high frequency operation.

Edit: The second circuit (thumbnail) uses a high-speed current-feedback type op amp which generally is less sensitive to stray input capacitance and less prone to oscillations (note lack of feedback capacitor), but has a slightly higher input offset voltage.

 

It's not easy to achieve the clean, high speed precision rectification you want.
Below is the LTspice simulation of a precision rectifier circuit that avoids op amp saturation and appears to work fairly well at 500kHz.
It has the advantage over some other configurations, such as the one in post #28, of requiring only two matched resistors (R1 and R2) for good amplitude match of the two halfs of the rectified wave.
C1 is needed to prevent high frequency oscillations in the waveform. Its value likely will have to be tweaked for the best waveform in the actual circuit.
The circuit will also require careful layout (preferably on a ground plane) and power supply decoupling with 0.1μF ceramic caps at the op amp pins (not shown) for best performance. It likely won't work well on a plug-in breadboard such as shown in post #27.
It uses high speed op amps to achieve the desired high frequency operation.

Edit: The second circuit (thumbnail) uses a high-speed current-feedback type op amp which generally is less sensitive to stray input capacitance and less prone to oscillations (note lack of feedback capacitor), but has a slightly higher input offset voltage.

View attachment 117329
View attachment 117327

Thank you crutschow for the help! As this is a school project, I'm only able to do it on a plug-in breadboard due to financial and equipment constrain. I'll try to do up both of the circuits on a breadboard tomorrow and show you the results! Many thanks!

 

I'm only able to do it on a plug-in breadboard due to financial and equipment constrain.

Then keep the leads short and be sure and add the 0.1μF decoupling capacitors from each op amp supply pin to common.
For that layout, the second circuit using the LT1259 current-feedback op amp may perform better since it's less sensitive to the large stray capacitance of a plug-in breadboard.

 

Then keep the leads short and be sure and add the 0.1μF decoupling capacitors from each op amp supply pin to common.
For that layout, the second circuit using the LT1259 current-feedback op amp may perform better since it's less sensitive to the large stray capacitance of a plug-in breadboard.

Hi crutschow, there are no more 0.1uF capacitors in my project room. Is it possible to use other value capacitors?

And I have no idea whether this breadboarding is correct to the second circuit as you've shown. Could you help me take a look? Many thanks.

Edit: I have inserted the diagram of the MCP6292

 

there are no more 0.1uF capacitors in my project room. Is it possible to use other value capacitors?

The value is not critical.
What other ceramic capacitor sizes do you have available?

And I have no idea whether this breadboarding is correct to the second circuit as you've shown. Could you help me take a look?

Sorry, I don't have the patience to trace out your circuit.
You'll have to try it and see if it works.

 

The value is not critical.
What other ceramic capacitor sizes do you have available?
Sorry, I don't have the patience to trace out your circuit.
You'll have to try it and see if it works.

There's 0.15uF & 0.47uF capacitor available.

Ok I'll try it out then! For this 2nd circuit, I've to use dual supply for the op-amps am I right?

 

There's 0.15uF & 0.47uF capacitor available

The 0.15μF will be fine.

Ok I'll try it out then! For this 2nd circuit, I've to use dual supply for the op-amps am I right?

Correct.
As shown, the circuit won't work with just one supply.

 

Hi gurus,

I may need your help again as I didn't manage to rectify my 500khz sinusoidal signal properly as shown below.

Is there any way to make the signal to rectify properly like this?

http://data:image/png;base64,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

This is the circuit I've used. I am using Microchip MCP6292 (http://ww1.microchip.com/downloads/en/DeviceDoc/21812e.pdf) and this project only can use 500kHz sinusoidal wave.

Please advice. Thanks in advance.