Re: [sdiy] High Voltage Opamps ?

[jhaible at debitel.net]

Michael Buchstaller <buchi at takeonetech.de> schrieb: 
> >Add a Tube output stage to your opamp !
> 
> Good idea. But simply adding the tube´s grid to the opamp output will invert the signal,
> not ?

Switch the opamp's input pins. On a TL080 (DIP 8), Pin 2 will be positive input,
and pin 3 will be negative input (for feedback).

> What kind of compensation ?

That's not easy, at least if you want to build a decent amplifier.
But if you only want to do DC and slow changes, you might try an opamp with
external compensation (LM301, TL080 etc.) and oversize the capacitor.

This whole thing doesn't need a tube, of course. Any transistor that can stand the
high voltage will do.

JH.




> 
> >I've seen headphone amps like this. While I wouldn't really want an opamp in a tube
> >HP amp, it should be ok for static and low frequency measurements.
> 
> Hmmmm.... I remember some old Philbrick schematics, where they made an opamp building
> block from 2 ECC´s - i built that once and made a simple (but working) Twin-T resonator with it...
> Maybe i could just use *that* as my opamp....
> 
> 
> -Michael Buchstaller