Logarithmic amplifier with 741 (CB7452E)

Found in Electronics Now from the 90s, this circuit can use any general-purpose transistor. The power supply must be symmetrical.

Voltage Controlled Amplifier (CB25145E)
This VCA was found in the July 1988 issue of Radio Electronics magazine. It uses an OTA op amp and...
Waveform Converter (CB6668E)
Found in US documentation, this circuit changes the waveform and phase of a sine signal. The...
Antenna Impedance Bridge (CB4122E)
Found in an American amateur radio documentation by the name of “antennascope” this circuit is...