[time-nuts] OP-Amps for 10MHz distribution...?
lists at lazygranch.com
Tue Feb 28 19:51:54 UTC 2012
You need to look at the driving impedance before you declare one
technology "quieter" than another. That is, you have voltage noise and
current noise. For low driving impedance, bipolar will be quieter since
current noise will not be significant, plus a bipolar will have lower
thermal noise. For high impedance, JFET may be a better solution.
Opamps are around 1nv/rootHz these days. That isn't all that easy to
Noise is proportional to the square root of the bandwidth, so less is
more. But that is broadband noise. I'm not sure about phase noise.
On 2/28/2012 10:41 AM, Bill Fuqua wrote:
> Discrete amplifiers are always less noisy than integrated amplifiers.
> If you want really low noise design a one with JFETs and Bipolar
> I am trying to understand the contribution to phase noise by the opamps.
> Perhaps the "threshold" is shifting and amplifier is being driven to
> I am new to this group but have had lots of RF experience and weak signal
> detection experience.
> Bill wa4lav
>> Date: Tue, 28 Feb 2012 07:34:09 -0500
>> From: Bob Camp <lists at rtty.us>
>> Very cool. How much power can you run through the device? Put another
>> way, if you drive it with +13 dbm do all the numbers get 5 db better?
>> I doubt very many of us will be worrying about weather it's below -153
>> at 10 Hz or not?
>> On Feb 28, 2012, at 5:42 AM, Bruce Griffiths wrote:
>> > The attached plot indicates the phase noise performance obtainable
>> with a wideband FET (OPA653) input opamp.
>> > With a 10MHz +9dBm input, the phase noise floor is around -163dBc/Hz
>> at 1kHz offset and around -154dBc/Hz at 10Hz offset.
>> > A quieter test source would be useful particularly for offsets below
>> > Bruce
>> > <OPA653PN2.gif>_______________________________________________
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> William L. Fuqua III P.E.
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