• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Regulating high voltage (up to 450V) has become as easy as a LM317!

Hi

in attach the stuff I am using
I have done some pcb.
Good regulation and good Ima on output
On board there is a reference fo elevation of filaments, in case


Walter
 

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  • HT_Var_schema.jpg
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Jan, it seems you have a specific FET in mind?

Just curious, Gerrit

No, but if I needed a HV CS I would search for a device that fills the specs and that would give me the voltage compliance and dynamic impedance I want. I definitely would not blindly select one of those current sources that are presented on a datasheet as if they are a device, and which I think has only as purpose to increase sales of that particular FET.

Jan
 
...and you have to ensure somehow that the DC current is not going into the AC source. Then again, I'm making all sorts of assumptions, so maybe this comment doesn't apply to your set-up.

Thanks for pointing this out Marcel. It's a simple, one port measurement, and yes I believe that energy is being reflected back into the VNA - interesting this is pointed out as a source of measurement error in a Keysight application note.

I have a "dynamic load" -- ZTX450/ZTX550 which is good to a few MHz. Will see.

Might just be better to break the loop and measure PM at 0dB, but impedance is so much easier.


Note that in subsequent correspondence, it was pointed out that the LM317 is a noisy CCS.
 
Walter, why not take the feedback from the output? That would make it a real good regulator, right now most of the LR8 performance is wasted because of the FET follower.

Jan


Hi Jan

honestly the test done on desk are fine. The level of ripple is very low and stability with different current is also fine
But I will check your suggestion, it is easy to do

Walter