This is the basic configuration of an operational amplifier sample & hold circuit. The FET and transistor are commonly used. The circuit is from an 80's documentation.
This circuit was published in the Ideas section of Radio Electronics magazine in August 1983. The...
This circuit was found in a 1966 EEE. It is intended for automatic switching of the measurement range of...
The first transistor can be the BF494 and the other BC548 on this MW radio found in a...