Suggestions on regulating -70v

Mark Johnson

Member
Paid Member
2011-05-27 3:27 pm
Silicon Valley
My suppliers don't stock 70 volt zener diodes but they do stock the NZX36, 1N5258, and 1N4753, all of which are 36 volt zeners. So you could build zener regulated, capacitance multipled supplies using MJE340 / MJE350 as series pass regulators. 6 components per rail.
 

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Robert Kesh

Member
2012-10-28 3:20 pm
if you have two secondaries, you can use a positive chip regulator "upside down" as it were, to regulate the voltage between the ground and the negative. you must form the ground point after both regs, not before

also, you can use a lower voltage regulator and attach zeners to the adjust to take it up, so long as the drop between Vin and Vout doesn't exceed spec, and you don't short the output by accident
 
if you have two secondaries, you can use a positive chip regulator "upside down" as it were, to regulate the voltage between the ground and the negative. you must form the ground point after both regs, not before

also, you can use a lower voltage regulator and attach zeners to the adjust to take it up, so long as the drop between Vin and Vout doesn't exceed spec, and you don't short the output by accident

do you have an example schematic for your first suggestion?
 
If you're using a 3-terminal regulator, just using a sufficiently large resistor on the Adj pin could work. Take a look at the application notes; there's a wealth of information there on power supply design.

Alternatively, this might be a case where shunt regulation makes sense. I have a hunch that could be electrically quieter than using a zener. I assume that a microphone needs very quiet supply rails.
 

Robert Kesh

Member
2012-10-28 3:20 pm
If you're using a 3-terminal regulator, just using a sufficiently large resistor on the Adj pin could work. Take a look at the application notes; there's a wealth of information there on power supply design.

Alternatively, this might be a case where shunt regulation makes sense. I have a hunch that could be electrically quieter than using a zener. I assume that a microphone needs very quiet supply rails.
I have always wonderd about the PSRR of a mic, and can never find any info. Luckily the standard 48V phantom power is easily regulated with a LM317HV
 
You can use the "2 Transistor Regulator" from Jones "Valve Amplifiers" -- the output voltage will be ~2x the value of the reference. It's good to around 40-50mA and very simple to implement.

[IMGDEAD]http://www.tech-diy.com/RegPowerSupplies/2TransistorRegulator/2Trans_Schem.gif[/IMGDEAD]

For more current use a Darlington transistor as the pass element.