This circuit that appears in several versions in this section and on this website was found in documentation from the 1980s. The transistors can be of any general purpose NPN type like the BC548.
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...