Simplistic MosFET HV Shunt Regs

[merlin el mago]

Both using only CCS load. Now I will add the SSHV2 & post de measurements.

 

[merlin el mago]

With SSHV2 + CCS load

 

[merlin el mago]

1st left pic 10x, 2nd right pic 1x probe.

 

[Salas]

1x don't use on HV, not only low bandwidth in probe but also low voltage abilities of probe.

 

[merlin el mago]

OK

 

[Salas]

So we can see some ripple with ghosting inside. Seems like some instability or noise. Experiment until cleaned result.

 

[merlin el mago]

That's adds the SSHV2. Only CCS load is clean.

 

[merlin el mago]

¿The scope measures a lot more ripple than the DVM?

 

[Salas]

You know the knobs scale. I can't read directly off the screen, its not a digital scope. If this CCS plate load does not like a CCsed reg and they react, use something else. Or try local decoupling, alternative Fets, higher value gate resistors, tubes etc. to see if it can get better.

 

[Salas]

There was also some ghosting in CCS load without the reg in the previous page though.

 

[merlin el mago]

4K7 resistive load
50mA SSHV2 CCS
68mVAC ripple
150Vout SSHV2
32mA load powr consumption
No CCS load used

 

[merlin el mago]

Scope not shows any kind of ripple with resistive load.

 

[Salas]

Trust the scope. You can't know what exact thing the DMMs see.

 

[merlin el mago]

 

[merlin el mago]

Could I use this K389V dual?

 

[merlin el mago]

I want to set the CCS load 12-13mA.

 

[Salas]

It should work for such as many mA. Or towards there. Available voltage across is little (VGS of MOSFET playing that role) that is why the JFETs don't reach their normal condition IDSS in that cascoded circuit you use as plate load. JFETs with small Vgs (off) give relatively more mA at low VDS across. Its shown in their curves. Reaching saturation faster than others.

 

[merlin el mago]

Salas I investigate the reason SSHV2 don't works very well with CCS load, in the schematic used the cathode bias used is a battery between the input & the grid. Could be the reason?

 

[Salas]

Could be. I haven't used the specific application to tell you for sure. Or if it works better with some variation.

 

[merlin el mago]

Attached the schematic used, not same tube nor resistors or B+