This elaborate mixer is from an Electronics Today International from the 80s. Operational amplifiers are common and resistors with no value determine the gain of the amplification steps.
This 12 or 13.8 V stabilized source is suitable for experimental FM transmitters that require...
This circuit uses a TL071 to differential amplify the signals from a microphone and thus reduce...
Found in Motorola documentation from the 90's, this circuit charges the capacitor with a constant...