The frequency of this circuit depends on C1 and, for the indicated values, it is 1 kHz. Equivalent operational amplifiers can be used, and the power supply must be symmetrical.
This is the project found in a 1981 publication, but it is still viable. It is a simple AM...
This 2-quadrant modulator circuit was found in the May 1988 issue of Radio Electronics magazine. The...
Found in Radio Electronics from May 1959, this transistor tester is quite sophisticated. The...