[time-nuts] Divider circuit for Rubidium Standard

Attila Kinali attila at kinali.ch
Sun Jan 10 05:01:34 EST 2016


Moin Bruce,

On Sat, 9 Jan 2016 21:36:35 +0000 (UTC)
Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:

> Splitting the resistor in 2 and ac coupling the emitters together
> reduces the effects of Vbe and/or base biasing mismatch allowing a more
> symmetric output and/or operation at lower input signal levels.The inductor
> reduces the high frequency variations in the total emitter current. It also
> reduces the tail current noise at high frequencies.


Thanks for the explanation!

One additional question: Why is the bias voltage for the two transistors
derived independently? In my naivite i would have used a single resistive
devider, buffered it with a large enough C and then split that bias voltage
off with a 3.3k resistor each. This would get rid off the bias mismatch.
(though not of the mismatch of the transistors)


			Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson



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