# Peak Voltage Detector

#### Hymie

Joined Mar 30, 2018
991
I have designed a circuit to capture/output the peak voltage of an input signal, with the output value the inverse of a negative input, such that the output is always a positive voltage, e.g. if the peak input signal is at minus 5V, then the circuit output will be plus 5V.

This is achieved by feeding the signal into a precision rectifier, followed by a simple peak-picker circuit.

Although the circuit works and only uses four op-amps, I’m wondering if there is a simpler solution – or if there is a single device available which performs this function?

A requirement of the circuit is for good accuracy, the peak output voltage should agree with the input at no more than 2% error.

#### LowQCab

Joined Nov 6, 2012
1,110
Probably not.
But we have not seen your Schematic.
The method, and possibly the automatic Frequency that you want to use for
the re-setting of the held Peak reading is very important.
.
.
.

#### Audioguru again

Joined Oct 21, 2019
3,544
I designed this circuit that works well for audio:

#### Attachments

• 17 KB Views: 17

#### MrAl

Joined Jun 17, 2014
8,481
I have designed a circuit to capture/output the peak voltage of an input signal, with the output value the inverse of a negative input, such that the output is always a positive voltage, e.g. if the peak input signal is at minus 5V, then the circuit output will be plus 5V.

This is achieved by feeding the signal into a precision rectifier, followed by a simple peak-picker circuit.

Although the circuit works and only uses four op-amps, I’m wondering if there is a simpler solution – or if there is a single device available which performs this function?

A requirement of the circuit is for good accuracy, the peak output voltage should agree with the input at no more than 2% error.
Why not show your circuit so we can take a look.

Most peak detectors that do not have to operate at very high frequency use an op amp to compensate for the drop of the rectifier diode(s) so the drop does not cause a loss of peak voltage, and one or more capacitors to store the peak. If you need the inverse of the voltage then you may need another op amp to translate the output voltage of the peak detector to the level and amplitude that you need on the very output.

Once in a blue moon you will run across a 'peak' detector that samples the sine input and holds the value of the peak or some other voltage at some other phase angle (other than at 90 degrees). That kind is capable of obtaining two measurements from one half sine wave rather than just one per half sine but it requires the use of a sample and hold circuit. You can take this even farther if you wish by using more sample and hold circuits so you get multiple samples over just one half sine input (and thus double that with the full sine 0 to 360 degrees). This gives you sub half cycle time resolution which you cant get with a regular peak detector at the expense of more complexity. It is a border line analog/digital technique.
Of course another method is to use an ADC (Analog to Digital Converter) and store readings and then do a little math to get the peak. Also gives higher time resolution at the cost of more complexity.

Last edited: