Re: [sdiy] High Voltage Opamps ?

[jhaible at debitel.net]

Add a Tube output stage to your opamp !
The tube will add some gain, so you can drive the grid with a few volts from a standard
opamp. Tube must be included in feedback loop of opamp. (Choose divider ratios to
keep the voltages at the opamp inputs in the opamp's common mode range.)
You will need some extra compensation of the opamp because of the extra gain of
the tube stage.
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.

JH.


Michael Buchstaller <buchi at takeonetech.de> schrieb: 
> Hello group,
> 
> a friend asked me to build him a computer controlled tube curve tracer. He
> is one of these strange audiophiles who wants to konw every silly stuff about the
> old tubes.
> 
> So, the conversion from the measured voltage levels via a voltage divider and feeding that
> into an ADC seems to be no problem.
> 
> I will have to build a regulated DC heater, but with it´s low voltages (1...15V) that will be no problem
> for any Opamp with a transistor follower in the regulated loop.
> 
> But, how will i create the high voltage levels ? Ordinary DAC´s output 0...2.5V or so, How do i convert that
> to 0...600V ? Are there Opamps for high voltages that i could use, or can i use some clever trick to
> work with low voltages on the controlling side ?
> Any hints of leads to suitable application notes would be more than welcome.
> 
> Thank you all !
> 
> 
> -Michael Buchstaller