is due to the curve tracers power supply collapsing.      As for the inverted or grid amplifier, the idea is a very old one. At least 70 years old. It is briefly mentioned (page 209) in Frederick Emmons Terman's Electronics and Radio Engineering, 1955, McGraw-Hill. (Bytheway, he was the father of Silicon Valley.)     Be sure to follow the Link of the Month in this issue, as Steve Bench covers this topic in great detail at his site.     I once designed a power amplifier that used this topology to relay the signal from the output tube's plates in a push-pull amplifier to the driver stage to allow a feedback loop to be formed, but I but I never built it. (Maybe I should for article fodder.) When the plate in the inverted amplifier is at a voltage negative to the cathode, it loses all of its rp and becomes a ultra-high impedance input. The grid, on the other hand, develops an extremely low "rp" (rg?). My aim was to use the grid as if it were the cathode and couple it to a conventional ground-cathode amplifier's cathode.
 What derailed this design path was an alternative circuit, the grounded-grid plate follower, which eliminated the need for the coupling capacitor and the huge negative power supply voltage. This circuit uses the plate as an input and the cathode as the output, which leaves the grid as the reference point. Like the cathode follower it does not invert the voltage phase of the input signal and it has a very low output impedance. Unlike the cathode follower, this circuit does not have unity gain output; in fact it has very little gain, roughly 1/mu. In addition, its input impedance is vastly greater than that of the cathode follower. What it does do rather nicely is allow large DC voltage shifts to be made.

Plate follower providing a feedback path
 In past issues, I have bemoaned the lack of a intelligent taxonomy of the basic tube circuits (and I have decried the general naming practice of tube circuits, i.e. no system). I proposed that the triode, MOSFET, FET, and transistor elemental circuits should be organized and named according to the following order: input, reference, output. Thus the grounded-cathode amplifier would be described as a grid-cathode-plate amplifier or GKP for short; a grounded-

Inverted amplifier providing a feedback path