[sdiy] HV Voltage translation

[Nicholas Gregorich]

Karl Ekdahl wrote:
> Hi list
> 
> I need some help amplifying a DC signal to voltages that is beyond the common opamp range, say 0-5V amplified to 0-30V for example. I was thinking that one of the easiest ways should be to use a opamp with a transistor in it's feedback loop but i cannot really seem to make that work. Any ideas greatly appreciated!
> 
> Karl
> 

Opamp input buffer into a common emitter then maybe a common collector 
output depending on desired output impedance. Now you've got new 
problems like crossover distortion and adding buffers between the gain 
and output stages to prevent loading and are on your way to designing an 
(discrete) opamp. ;)

A vactrol circuit could work, but with a different set of problems.

Nick.