The purpose of this circuit is to check the linearity of SSB amplifiers. The circuit was found in an old documentation for hams. The diode is a general purpose detector type.
USB58xx and USB59xx Devices Integrate a 2:1 Multiplexer to Support Reversible Connection of USB...
This circuit was found in a Popular Electronics of the 90s. The resistor R4 determines the load...
This CMOS circuit divides the frequency of a rectangular signal up to 2 MHz by 6. The supply...