Voltage to frequency converter (CB8928E)

Found in ancient American documentation, this circuit uses an operational amplifier of the time, which is uncommon today.

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PWM motor control (CB7999E)
This configuration of PWM control with the LM317 was found in a Popular Electronics from the 90s....
Audio Line Amplifier (CB4769E)
We found this circuit in a European publication from the 1990s. Transistors are still common types...
Temperature control 555 (CB9469E)
This circuit was found in Signetics documentation from the 90's. The circuit performance curve is...