This circuit with a differential pair was found in the August 1974 Radio Electronics magazine. The frequency is determined by L1 and the variable capacitor.
This circuit was obtained in an Electronics World of 1969. It is a crystal oscillator with a 100...
This circuit, shown in the figure, consists of a variable gain amplifier with differential input...
This circuit was found in the July 1992 Radio Electronics magazine. Sensitivity adjustment is made...