We found this circuit in a 1977 National Semiconductor Databook. The circuit can use other FETs like the BF245 and has an input impedance of 10 megohms. The circuit gain is unitary.
This circuit is recommended for alarm systems since it has a good output stage. The circuit is...
) Suggested by Philips in a 1968 documentation this circuit has very high 10 ohm on-load voltage...
No information is given about the transformers in this circuit suggested by Motorola in a 1968...