I think I've got the key bits in there... like the common mode feedback the right way around.
It's a diff amp, but most scopes have a SE front end. So, like most scopes, the position knob goes to -in and signal to +in. A preamp might be a good idea for the more sensitive ranges.
The 2N5179 pair should be fast enough that I get the ~20 gain I want up to
50MHz or so. '3904's are kind of pokey for this, but as emitter followers, who cares. That just leaves the hope that the C1569's are as fast as claimed. Overall, I should have enough current flowing to reach within a few clicks of fT. But what do I know, I haven't built a wideband circuit like this before...And if not, I could replace the bastards with a 6CL6. That'll show 'em.
Tim
-- Deep Fryer: A very philosophical monk. Website @
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