In the figure we have a simple way to have a peak bargraph indicator. The amplifier is of the audio type, but operational ones can be used. The circuit is from Radio Electronics from March 1980.
This amplifier from 100 to 150mW was found in a Japanese documentation from 1967. The circuit uses...
This circuit is from a manual of JFETs and can be implemented with the BF245 and for the bipolar...
This source of some amps for voltages up to 40 V was found in an Italian magazine Elettronica...