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Old 4th August 2012, 07:46 AM   #11
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Join Date: May 2002
Location: Great City of Turnhout, Belgium
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Originally Posted by CBS240 View Post
I do this often and it works great. But like Jan said, any variance in current pulling off of the voltage reference will vary the reference. So I like to use it in this manner...

Cascode the low Gm J-fet with the high Gm J-fet to get a more acurate Idss. Use a J-fet gate as the load on the voltage reference to steer the differential. (the N-Jfet and the P-Jfet act like a diff amp in this arrangement) If much higher output voltage is needed, you can always add another cascode to the J201. Way better than using noisy Zeners for a voltage reference IMO.

Nice. Any measurements for us to compare to a purpose-designed voltage reference driven by a CS? I would be interested in Zout over freq and nosie levels.

Note to Phisci: this is also a reference build from a current into a resistor, but the difference with your idea is that here there is a negative feedback loop that modifies the current source 'strength' to compensate for reference changes with load changes (and a few other things), and thereby stabilizes the ref voltage.

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Last edited by jan.didden; 4th August 2012 at 07:49 AM.
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