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.
This strobe light circuit with xenon lamp was found in a 1995 documentation. The circuit is...
This small stereo amplifier for headphones was found in a documentation on integrated circuits from...
This is the basic configuration for using a moving bar indicator or bargraph using the LM3914...