This commercial transistor radio was manufactured by RCA in the 1960s. The circuit has only 4 transistors and is powered by a voltage of 9 V with an audio power of 20mW.
This is the basic configuration of the LM339 as a comparator, requiring a 3k (3k3) pull-up...
This circuit uses two operational amplifiers, which can be of the type 741, in a full wave...
We found this circuit in a Texas Instruments documentation from 1973. Other operational amplifiers can...