[time-nuts] Build my own dist. amp ??

[Bruce Griffiths]

BriMDavis at aol.com wrote:
> Bruce Griffiths wrote:
>   
>> That is a very effective way of elevating the phase noise floor.
>> Its usually far better to amplify the input and then split the output
>> maintaining a gain to the splitter outputs of at least 0dB.
>>
>>     
> As I already explained the last time you mentioned this, 
> I am well aware of noise floor limitations when operating 
> an LO or clock at reduced signal levels.
>   
Have you actually estimated the resultant phase noise floor with 0dBm
output??
An optimistic estimate can be done using the noise figure at the
frequency of interest.
>  
>  It is nice to keep the drive levels as high as possible; 
> however, as long as the overall system noise floor is not 
> impacted, it really doesn't matter if the reference level 
> drops somewhere along the way.
>   
When is a noise penalty of around 30dB (for the better sources) not
significant?

>  
>   
>>> Some data sheets contain this information at spot frequencies; 
>>> this one does not.
>>>   
>>>       
>> Very few datasheets from Maxim specify much about the noise
>> characteristics of such devices.
>>
>>     
> Perhaps we are suffering from a language barrier here.
>  
>  When I look at all 21 devices in their "VCOs/VCO Buffers" 
> parts category, the only ones _without_ noise specs are the 
> very parts about which I am asking, the MAX274x family.
>  
>   
Very little useful phase noise data is given (for a distribution
amplifier application), particularly for low offset frequencies.
For example MAX9989 only gives a spot phase noise at 100MHz output for a
1500MHz input.

I was also referring to the lack of low frequency noise data for devices
like the MAX477.
Maxim aren't alone in this.
> Brian
>  
>  
>   

Bruce