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.
The basic application of a 4017 as a sequencer [10 steps] is shown here. In this same part, you...
The circuit presented uses an integrated circuit Sanyo, not very common in our day. This amplifier provides...
This circuit is from a 1977 publication for radio amateurs presenting a crowbar protection. The...