The indicated circuit uses an unusual buffer from National Semiconductor. The frequency is given by resistors R1 and R2 as well as capacitors C1 and C2.
Other operational amplifiers can be used in this conventional filter that rejects only one...
The integrated circuit used in this' 90s amplifier is not very common today. The supply is 24 V,...
This squelch circuit is placed at the input of the single receiver audio amplifier stage. Its...