Hi,

I'm working on a project right now where I need a precision rectifier and a peak detector. For the precision rectifier, I was planning on using a diode and op-amp. For the peak detector, I'm a little confused. I've a some Googling, but I'm not sure how to design the peak detector. Sensitivity is a BIG issue, I need it to be pretty sensitive. 0.05V-0.1V at low frequencies not exceeding 60Hz.

I attaching the two circuits I was thinking of implementing. I'm not sure how to modify them for my specific purposes?

I was also thinking of this http://freecircuitdiagram.com/2008/09/07/precision-half-wave-peak-detector/ which claims to be precise under 100mV, but it uses a LF351 which appears to be discontinued.

 

Hi,

I'm working on a project right now where I need a precision rectifier and a peak detector. For the precision rectifier, I was planning on using a diode and op-amp. For the peak detector, I'm a little confused. I've a some Googling, but I'm not sure how to design the peak detector. Sensitivity is a BIG issue, I need it to be pretty sensitive. 0.05V-0.1V at low frequencies not exceeding 60Hz.

I attaching the two circuits I was thinking of implementing. I'm not sure how to modify them for my specific purposes?

I was also thinking of this http://freecircuitdiagram.com/2008/09/07/precision-half-wave-peak-detector/ which claims to be precise under 100mV, but it uses a LF351 which appears to be discontinued.

What's your question?

I've messed about with precision rectifiers. They're not as straightforward as the pretty schematic you uploaded.

Can you reveal a bit more detail as far as what you're aiming to do with all these devices? That'll give us a better clue as to what your options are.

Paul

 

Have you seen this http://sound.westhost.com/appnotes/an001.htm
Also I think it would help if you amplified the signal before sending it to the Precision Rectifier. As they are not good at low voltage levels.

 

ZXCT1041 can be used as a precision rectifier:

http://www.diodes.com/datasheets/ZXCT1041.pdf


http://www.physics.mcmaster.ca/electronics/appnotes/ZXCT1041 Precision Rectifier an55.pdf

 

Nevermored,
You attached a very bad circuit.
The first circuit has nothing to discharge the capacitor so it will not work properly.

All opamp circuits in this thread do not show how the opamps are powered. Most of the circuits need a dual-polarity power supply.

 

Hi,

I'm working on a project right now where I need a precision rectifier and a peak detector.

You can have this one I designed some years back for a wide band (about 20 - 200 kHz) AC meter. The circuit shown creates a negative voltage, just reverse the polarity of the diodes if you want a positive output. Use both 1N914 diodes if you only want low frequency performance. I used a current source (not shown) to discharge the peak hold cap (the 1uF cap). Add a big resistor across it for discharge such as 2 MEG or similar.

 

...............................
The second circuit makes a "super diode" that has a high forward voltage drop because the diode is not inside the negative feedback loop of the opamp.
.......................

The "Superdiode" circuit does have the diode inside the feedback loop, so I don't understand your statement.

 

The "Superdiode" circuit does have the diode inside the feedback loop, so I don't understand your statement.

OOps, yes you are correct. I looked at it too quickly.

 

have a look at the application examples in this PDF for the LM3916 VU Meter IC >> https://www.national.com/ds/LM/LM3916.pdf