Simple shunt regulator... but how much current?

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Tom Whitworth:
Greetings,

I want to make a simple shunt regulator to change 12V+ DC to 5V+ DC for a microphone active filter stage. No big deal except I am missing one piece of the puzzle. What is the circuits current draw?

Could someone take a stab at what the current draw might be for this? I am interested in the stage that shows 3 op amps.

The schematic shows +5V on one of the mic pins but my radio does not provide that so I have to develop it somewhere else.

Just google md-100 schematic / images and you should be able to find the schematic.

Robert Holsti:
just use an lm7805 3 terminal regulator. 

Tim Shoppa:
It's just two 2-section op-amps. Figure a few mA quiscent current for each op-amp, another few mA for the bias resistor network, and dynamic current is very unlikely to ever get over 40mA or 50mA. This is "1/2W zener diode" type territory.

You might check inside the pre-amp and see if the electrolytics etc. might be rated for 14V or higher. Because the op-amp (upc4572C) itself is rated for 14V, in which case you would be fine running it off 12V or 13.6V directly.

Dieter Kuespert:
To be on the save side I would calculate with 100 mA.

Tom Whitworth:
Quote from: KH2BR on July 25, 2014, 09:13:58 AM

just use an lm7805 3 terminal regulator.  


That is an excellent idea.

Quote

Because the op-amp (upc4572C) itself is rated for 14V, in which case you would be fine running it off 12V or 13.6V directly.

I have seen warnings about NOT using this microphone with say Kenwood which use a +8V. Maybe there just being cautions.

Many thanks to all!  :)

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