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 with two 555s was found in the Encyclopedia of Electronic Circuits volume 5 of 1995....
This circuit was obtained in a European documentation of the 80's. The circuit uses common...
This circuit is from the 1974 Motorola Unijunction Trigger Circuits for Gated Thyristor. The triac...