[time-nuts] reference oscillator input circuit

[Bruce Griffiths]

jimlux wrote:
> Javier Herrero wrote:
>> El 09/12/2010 15:21, jimlux escribió:
>>> Javier Herrero wrote:
>>>> Good to know. Now I see what not to use :) I was supposing that the 
>>>> hysteresis would not be so high being low voltage signalling, and 
>>>> since they are used for low-jitter applications. But really I've 
>>>> only used them for their intended main applications :)
>>>
>>>
>>> hysteresis is in the 100mV minimum range, and max peak amplitude is 
>>> in the 0.9 to 1 Volt range (they'll have a bias point a bit over a 
>>> volt, and a lot of them do not do well at all if you swing close to 
>>> the supply rail)
>>>
>>> Maybe with external clamps and over drive it.
>>>
>> Yes, I was thinking in that way. But surely they are better solutions :)
>>
>
> hence my question to the list..
>
> I'm going to gather all the responses and summarize them for the list 
> later today.
>
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Since noise modulation (power supply and device noise) of device 
parameters (eg collector base capacitance) can be a significant source 
of phase noise adding some emitter degeneration in a long tailed pair 
and shunting the collector load resistors with inductors (eg a 
transformer winding) should be an effective way of reducing such phase 
noise. A capacitor shunting the collector load can also be effective in 
reducing the circuit bandwidth closer to the optimum and desensitising 
the circuit bandwidth to device parameter variations. However avoiding 
high Q parasitic resonances with the output inductors (or transformer) 
will be necessary.

Bruce