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Discussion Groups | Comp.Arch.Embedded | Nulling a long-tailed pair

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Nulling a long-tailed pair - Spehro Pefhany - 2012-09-26 12:19:00

Okay, I have a long tailed pair (actually a Gilbert cell differential
output), presumably diffused resistors to Vdd, and there's a DC offset
and tempco of that offset. Current is about 1mA on each side. 

I tried nulling the differential output voltage by adding a high
resistance to the lower side to Vdd, and the tempco seems about the
same magnitude, but the sign flips. 

Is this to be expected? Lucky chance? Experimental error?

Re: Nulling a long-tailed pair - Spehro Pefhany - 2012-09-26 12:19:00

On Wed, 26 Sep 2012 12:19:06 -0400, Spehro Pefhany
<s...@interlogDOTyou.knowwhat> wrote:

>Okay, I have a long tailed pair (actually a Gilbert cell differential
>output), presumably diffused resistors to Vdd, and there's a DC offset
>and tempco of that offset. Current is about 1mA on each side. 
>
>I tried nulling the differential output voltage by adding a high
>resistance to the lower side to Vdd, and the tempco seems about the
>same magnitude, but the sign flips. 
>
>Is this to be expected? Lucky chance? Experimental error? 

Oops, wrong newsgroup. Sorry!