how much achievable gain with UGS?

[Stefanoo]

Hi,

I am curious: is it possible to achieve up to 60dB gain with a UGS voltage gain stage?

[amhlee]

I do not think so..... I have tried 5x which is the same on the X2

[Nelson Pass]

As I recall, a stock UGS does not have an open loop figure
anywhere near that high. You can modify it for that tho,
(he asked, wondering why you would want that)

[Stefanoo]

Originally Posted by Nelson Pass

As I recall, a stock UGS does not have an open loop figure
anywhere near that high. You can modify it for that tho,
(he asked, wondering why you would want that)

yeah I made the calculation and OL is not more than 17-20dB.
Eventually more gain could be achieved by adding a second buffer stage and closing the loop with that, although it would be nice to have very linear jfets, as good as Jk74/170, but with very high transconductance to be able to achieve that sort of gain with just one stage .

In this fashion anyways OL will go high enough to achieve 40-50dB gain.

Nelson I have a question though regarding phase response:

I am sure you have the possibility to make frequeny and phase response of your gears.
What do you consider a good phase response?
I know there is correlation with phase delay and fidelity on the reproduction and phase vs. OL/CLG i.e. FB gain as well.

Should the phase be as linear as possible? Should it be as close to 0 as possible?
I know the latter is the ideal although pretty impossible

Should I look at log(phase) or linear scale across let's say 10Hz 10MHz?

I am taking measuraments with the Vector analyzer HP4395A and using the Tek scope MSO9000 the 1Ghz mixed signal scope.

I am interested to know what you think about phase response.