Need Negative High Voltage Regulator Circuit

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You get a rejection of 50dB instead of 70dB because you didn't use the normalized unity stimulus for the Bode plot: you used 12, which represents a penalty of more than 20dB.

Thank you Elvee. Copied your interesting suggestions and I'll be back for small details if you don't mind. I will redraw a proposed circuit for my particular needs and try to find suitable transistors and MOSFET.

I am really a newbie to LTspice and so, could you please tell me how to instruct LTspice to plot correctly the -70dB as your plot ? I couldn't find such a setting for

normalized unity stimulus for the Bode plot...

Is this an LTspice setting or is it that my input generator signal needs to be changed, when yo say "you used 12" :confused:


Kay Pirinha,

Otherwise I'd recommend a Maida style regulator

what is a Maida style regulator ? Could you please be so kind to post a sample or link to it ?
 
Is this an LTspice setting or is it that my input generator signal needs to be changed, when yo say "you used 12" :confused:
You need to enter "1" in the amplitude box, unless you know exactly why you need to enter a different value, see below


Kay Pirinha,



what is a Maida style regulator ? Could you please be so kind to post a sample or link to it ?
A Maida is definitely better than a straight monolithic regulator used outside its comfort zone, but the main pass element remains the VR, even inside the cocooning and protection of discretes, and as such is much more vulnerable to abuse than a fully discrete voltage regulator designed for the target voltage/current combination.
In addition, the Maida is not exactly a LDO, quite the opposite in fact.

The simple 2 transistor example of this thread doesn't reach the performance level of a Maida, but there are alternatives: I have also described other series regulators that are a bit more complex, but have performance on a par with Maida's.
If really top performance is required, the best option is a discrete pass element combined with an opamp and a good reference.
It sounds complicated but it needs not be, and it offers better performance than a Maida, combined with the robustness of discretes
 

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