We found this receiver circuit for modulated light in a 90s Popular Electronics. Equivalent audio amplifiers can be used. Transistors are commonly used.
This oscillator has the output sine waveforms stabilized by a MOSFET. Equivalent types can be...
We found this synchrodyne receiver for the medium or short-wave band in the Radio Electronics...
This amplifier is suggested by Sanyo, for radio and recorder applications and makes use of a...