[time-nuts] EFC Input pin impedance for the HP 10544Aand10811-6011

Don Collie donmer at woosh.co.nz
Mon Oct 29 04:20:29 EDT 2007


Surely the only impedance we`re concerned with is that at DC, since it`s 
only an adjustment. The input would look like 200K, in series with a 
constant voltage source  [zero resistance ] of 6.4 Volts.
Cheers!,..........................................Don C.


----- Original Message ----- 
From: "Bruce Griffiths" <bruce.griffiths at xtra.co.nz>
To: "Don Collie" <donmer at woosh.co.nz>; "Discussion of precise time and 
frequency measurement" <time-nuts at febo.com>
Sent: Monday, October 29, 2007 9:01 PM
Subject: Re: [time-nuts] EFC Input pin impedance for the HP 
10544Aand10811-6011


> Don Collie wrote:
>> So, what *is* the input impedance?
>> Cheers,...............................................Don.
>>
>>
> It depends on the frequency.
>
> Network is complex 20k in series with 100-200pF plus another 20K to
> signal ground plus a few pF shunt C from the varicap to ground (a few
> pF) for the 10544A as a first approximation.
> For the 10811 100K in series with the 100pF varicap plus a few pF in
> paralle with 100K to signal ground.
>
> Bruce 




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