This very high input impedance JFET circuit was found in the 1995 Encyclopedia of Electronic Circuits Volume 5. The JFET is a general-purpose transistor as is the output transistor.
This circuit uses two light-activated SCRs or LASCRs, uncommon components today. The power depends on...
I found this circuit in a Popular Electronics from November 1999. The magazine is no longer...
Other series amplifiers such as the MC3301, MC3401 and LM2900 can be used on this circuit. We...