Half wave vs peak detector circuit

[onceinalifetim]

hello

I would like to know what is the different between half wave rectifier circuit and peak detector circuit..
as what i know from half wave.. it only take the positive wave only..
then what about peak detector ??

 

[NascentOxygen]

The half wave delivers, say, the positive half cycles. Between those half-cycles it delivers nothing, i.e., it delivers zero volts.

The peak detector holds its value, so it doesn't deliver anything recognizable as half-cycles. Between the peaks of the AC it delivers the same voltage as the last peak. Instead of half-sinusoids, it delivers a roughly steady level, equal to the peak value of the most recent positive half-sinusoid.

For further detail, google.

 

[onceinalifetim]

do they work the same way? thanks for the reply

 

[FOIWATER]

A peak detector should do something more along the lines of this (this one is self resetting, it doesn't need to be! it might just hold the peak, that's what 'traditional' ones do)

They don't work in exactly the same way although they have similar components. The peak detector for any practical purposes usually requires an op amp. You can build one without an op amp, but you will not detect the peak as you will lose some voltage across the diode which prevents the 'peak' from discharging. The op amp can be used to compensate the diode drop. http://en.wikipedia.org/wiki/Precision_rectifier

Please check out this thread about a peak detector build here:

https://www.physicsforums.com/showthread.php?t=713307

 

[NascentOxygen]

do they work the same way? thanks for the reply

That depends on the application. There are places where you could replace one by the other, but mostly not.

The peak detector has already begun the process of "smoothing", whereas the half-wave rectifier shows no smoothing.

 

[onceinalifetim]

the reason why i ask because I am currently working on a autoguilded vechile project and am doing the sensor circuit... my PIC need DC signals.. so i need to change AC to DC.. that why am thinking to choose half wave or peak detector..