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[AMPS] strange idling current

To: <amps@contesting.com>
Subject: [AMPS] strange idling current
From: measures@vc.net (Rich Measures)
Date: Thu, 18 Mar 1999 11:12:27 -0800


>>which is why one puts c. 100k-ohm resistors in series with the input 
>>pins.  
>
>Not if you want the best temperature stability. Because input offset and
>bias currents vary with temperature, using 100kohm series resistors
>makes it worse:the variation in input offset currents give bigger offset
>voltages. A smaller resistor (1k?) should be enough to kill the oscillation
>without running into that problem.
>
?  osc. pales in comparison to the rfi problem.  To pass the 2m handheld 
test, it takes a fair amount of R at the input pins.  A current gain of 
over 500k is nothing to sneeze at.  .  

>But I don't like 723s anyway. 

?  According to my Fluke, the 723's excellent performance in the pos. 
floating screen reg.  is not a fluke.  The temp. stability appears to be 
excellent.  

>An interesting question: How long are they
>going to be around? They are an old design, on an old process. The trend is
>towards 3 terminal regulators of higher performance; I wouldn't design a 723
>into anything on the basis of its age now, and the replacement situation in
>few years.

?  so buy ten and toss 'em in the bin. 
>
-  later, Peter


Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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