This circuit was found in RCA documentation from the 1980s. The circuit uses LDRs of the time and the 50 uA instrument has zero in the center. R1 and R2 may have 2k2 and R3 10k typically.
This low power circuit for the FM band was found in a spy book from the 90s. The tunnel diode is...
This 3-decade operating range VCO was found in a 90s Popular Electronics. The circuit uses...
This circuit was found in an Electronic Design from the 90s. Operational amplifiers admit modern...