We found this transistor circuit in a 1967 General Electric documentation. The circuit makes use of components that can still be easily found on the market, and the SCR may be a 106 type.
The circuit whose characteristics are given in the graph uses two transconductance operational amplifiers...
This circuit was found in the Radio Electronics magazine in an article about emitter-coupled...
This circuit was obtained from an 80s factory manual. The integrated circuits used are uncommon...