We found this circuit in a Maxim documentation from the 90s. The 4-channel circuit uses a component of the time and has a supply current of only 6 uA.
This circuit using an operational amplifier was found in old American documentation. It can be...
If the circuit oscillates, emitting sound, it is because the transistor is good. This simple...
Like the previous circuit, this is used in the analog part of the telephone lines. The same...