For the simple peak detector below, what are some guidelines in choosing the value for the capacitor?
http://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/peak-detector/

 

Hello,

the value of the capacitor for the dector depends on the speed versus the accuracy.
A small capacitor will make it fast, but leakage will let the voltage drop.
A large capacitor will make it slow, but it will keep the maximum value much longer.

Bertus

 

Thanks for the answer!
I think time constant RC is what relating to speed and accuracy here?
With RC is small, it will charge and discharge fast.
Is there a detailed treatment of this? I tried to search but couldn't find a good one.

 

Hello,

A peak detector is used for keeping the maximum value of a signal.
An envelope detector will follow the changes in signal.
The following pdf will give you more info on the envelope detector:
http://educypedia.karadimov.info/library/tut331_04am_dem.pdf
Page 6 will tell you about the effects of the RC time.

Bertus

 

Vc=5(1-e^-t/RC)

 

Actually, I am using the structure (peak detector) as a rectifier. So, I think there should be a balance here.

 

The simplistic peak detector shown in chapt 3 is missing a crucial element, which is a discharge path for the capacitor. The effect of the discharge path (load) must be factored into the charging time, as well as the discharging time...