We found this circuit in a technical documentation for the National Semiconductor LM3909. The circuit consists of a low consumption continuity tester powered by a single battery.
We found this frequency meter circuit in a 1974 documentation. The circuit is powered by 12 V and...
This high gain small signal amplifier circuit was found in an old publication on transistors....
This circuit can be used with input voltages up to 750 V, regulating the current between 200 uA...