[sdiy] current mirror for NPN expo?

[Paul Perry]

Quite apart from the capacitor matching question, I would think that to 
exactly mirror transisitors, one would need the transistors to be fairly 
closely matched.
Maybe the EEs can comment.

paul perry Melbourne Australia

----- Original Message ----- 
From: "dan snazelle"

> that is how i ended up trying it...however the pitch is not exactly the 
> same on the second core...even though the part values are the same...i 
> will keep working at it
>
> thanks
>
>
>
>
> On Sep 19, 2011, at 12:15 PM, David G Dixon wrote:
>
>>> can anyone point me towards info on how to use ONE NPN EXPO
>>> to drive two vcos?
>>
>> Can't you just mirror the current-sourcing one?  I.e., tie its emitter to
>> the other two, and connect its base to the other current-sourcing one? 
>> You
>> should be able to replicate the current as many times as you want this 
>> way.
>> I did it with five transistors in a four-pole filter once; it worked a
>> treat.
>>
>>
>
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