Found in a 1992 book, this circuit is intended for operation with audio signals. Equivalent operational amplifiers can be used. The optical coupler is an unusual type today.
This circuit was found in a Mullard transistor manual from 1960. Note the symmetrical power...
This amplifier step with a transistor has an input impedance of 100k to 10 M. The transistor can be any...
I found this little signaling transmitter in old American documentation. The circuit has a good...