The configuration shown allows to obtain a high voltage gain for FETs. FETs can be BF245 or MPF102. The circuit is from the 1977 National Semiconductor FET Databook.
This simple circuit controls the signal amplitude through a photoresistor optical coupler. The...
This circuit can be implemented with standard photodiodes consisting of a two input optical AND gate....
In the figure we have the basic configuration of an operational amplifier for audio signals. The...