This peak detector has a memory to prolong the response. The circuit is from American documentation from the 1980s. The supply does not have to be symmetrical.
In the figure we have a bistable multivibrator using an operational one. The circuit is from old...
This is another of the Star Trek red alert circuit that you can find on this site. We took this...
This circuit for testing zener diodes by lifting their curve on an oscilloscope was presented in...