Found in a 1964 Electronic Design this circuit compares two signals by providing the inverse of the algebraic sum of their frequencies. The circuit can be made with modern equivalent transistors.
This circuit was found in a 1967 American documentation. The switching diode (tunnel) used is an...
This circuit was found in a 1975 documentation. Operational amplifiers must have a symmetrical source and...
The diagram shown was found in a 1975 active filter manual. The tuned frequency range depends on...