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 bargraph-type circuit employs a not very common integrated circuit today, but can be adapted...
May 2017 - This new Ricoh 4 A current device is now available from Mouser Electronics. The device...
This modulator circuit can be used in AM transmitters up to about 10 W of power. The TDA2002 must...