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.
In the original application of this circuit, from a 1985 documentation, we have only two entries....
This circuit, found in Texas Instruments documentation from the 90's, provides a voltage reference of...
We found this circuit in a 1982 publication. This source allows an adjustment of the output...