please suggest a pass element for superreg(5V, 60ma max)

agent.5 · 8th June 2005, 09:05 PM

How to choose a pass element for the Jung Super Reg type circuit?

I am designing one with:

precision, ultra low noise voltage reference
--> rail-to-rail, ultra low noise op-amp
--> pass element

Nothing special here really. How do one determine which pass element to use (low voltage and low current requirement)?

Is very low noise a requirement of the pass element? If so, I am thinking that I can parallel a bunch of super low noise JFETs as pass element.

AndrewT · 9th June 2005, 07:51 PM

Hi,
does Jung have a current limiter?
Then you choose to suit either 5v * 60mA = 300mW dissipation,
or 5v * short circuit current = BIG dissipation.
The first option allows you to choose any BJT with a Pmax of about a watt with a clip on heatsink in case your fuse does not blow.
The second option means choosing a med power BJT with hi current capacity and large enough heatsink to prevent destruction until the fuse does blow.

I don't think that low noise BJTs matters in your context.

AndrewT · 9th June 2005, 07:54 PM

Hi,
rail to rail is not required for Jung, he has already arranged for the necessary correction without this requirement.

Using rail to rail compromises many of the other attributes of the opamp and my affect your overall performance.

agent.5 · 9th June 2005, 08:03 PM

Thanks

8th June 2005, 09:05 PM	#1
agent.5 diyAudio Member Join Date: Aug 2003 Location: San Francisco, CA	please suggest a pass element for superreg(5V, 60ma max) How to choose a pass element for the Jung Super Reg type circuit? I am designing one with: precision, ultra low noise voltage reference --> rail-to-rail, ultra low noise op-amp --> pass element Nothing special here really. How do one determine which pass element to use (low voltage and low current requirement)? Is very low noise a requirement of the pass element? If so, I am thinking that I can parallel a bunch of super low noise JFETs as pass element.

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9th June 2005, 07:51 PM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, does Jung have a current limiter? Then you choose to suit either 5v * 60mA = 300mW dissipation, or 5v * short circuit current = BIG dissipation. The first option allows you to choose any BJT with a Pmax of about a watt with a clip on heatsink in case your fuse does not blow. The second option means choosing a med power BJT with hi current capacity and large enough heatsink to prevent destruction until the fuse does blow. I don't think that low noise BJTs matters in your context.

9th June 2005, 07:54 PM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, rail to rail is not required for Jung, he has already arranged for the necessary correction without this requirement. Using rail to rail compromises many of the other attributes of the opamp and my affect your overall performance.

9th June 2005, 08:03 PM	#4
agent.5 diyAudio Member Join Date: Aug 2003 Location: San Francisco, CA	Thanks