Has anyone else tried these circuits?
I have built 2 examples, a 9 MHZ AGC controlled amplifier and a 20 dB wideband amp for a noise cancelling system.
BIG problems! The diode string in the source of the FET always biases the J310 OFF.
Result, no gain or a loss!!!
It took me an hour or two to twig what was going on. The trouble is that I cannot see how it can possibly work when the gate is referenced to ground. It is equivalent biasing off a valve!
Not only that, but the AGC circuit published at the same time had extreme instability in the front end of the AGC amplifier. I am a VERY experienced electronics person (60 years) and was unable to find any obvious reason for this.
SO Now I have actually began to lose faith in one of my favourite engineers.
Or, have I done something really stupid in my old age.
FYI the circuits were built "dead bug" style with extensive shielding and full decoupling.