This circuit is from a 1980's documentation for telecommunications. The circuit is used in SSB and the diodes must be suitable types for the application. The audio input is low impedance.
Atmel's ATmega 324PB microcontrollers available from Mouser Electronics are RISC-based...
This circuit was obtained from an English magazine from 1979, but can be easily assembled...
This constant current source from a 1980 publication can be used on a battery charger. Transistor Q1 may...