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 consists of a traditional version amplifier with complementary output transistors...
This circuit is from a manual of linear integrated circuits of the 80s. The operational is of the...
Also suitable for use as a noisy alarm, this Morse Code or telegraph practice oscillator was found...