[time-nuts] About HP10544A

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Mar 8 16:04:00 EDT 2009


Didier wrote:
>   
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com 
>> [mailto:time-nuts-bounces at febo.com] On Behalf Of Bruce Griffiths
>> Sent: Saturday, March 07, 2009 8:48 PM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] About HP10544A
>>
>> Scott Newell wrote:
>>     
>>> At 07:41 PM 3/7/2009, Tom Van Baak wrote:
>>>
>>>   
>>>       
>>>> I know *late* model 5245L counters used the 10544A oscillator.
>>>> Perhaps others in the group can provide other examples and 
>>>>         
>> then you 
>>     
>>>> can head off to the online manual sites and grab the info you need 
>>>> from the PDF files.
>>>>     
>>>>         
>>> My 5345A has a 10544A.
>>>
>>>   
>>>       
>> Scott
>>
>> The 10MHz buffer is merely a cascade of 3 ECL line receivers.
>>
>> Bruce
>>
>>     
>
> Bruce,
>
> How much isolation can on expect to get from that kind of buffer?
>
> Didier
>
>
>   
Didier

The 5345A buffer is actually a CC stage feeding a CB stage with a CE
(with series feedback) output stage.
Total reverse isolation will probably be somewhere in the vicinity of
100dB or so.
However coupling via the bias circuitry will reduce this somewhat.

Cascading 3 ECL line receivers (longtailed pair plus output emitter
follower buffers) in a single package as in the 5370A should achieve a
reverse isolation of 60dB or so per stage, but package parasitics and
coupling through the internal bias regulator etc will limit this to a
somewhat lower value.

Bruce




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