This simple step of low power audio is from a 1975 documentation. The transistor can be a BC548, and the transformer of the type found in small transistor radios and recorders of the time.
Indicated by a Popular Electronics of the 90s originally to measure the light determining the exposure...
Other operational amplifiers series, such as the MC34072, MC34074, MC35071, MC35072, MC35074 d...
Found in American documentation, this circuit shows how to polarize a FET in bootstrap mode. The...