[time-nuts] Opamp Phase noise: OPA653 additional measurements

[Bob Camp]

Hi

My *guess* is that your 1Hz data may be as much from ambient changes as from the op amps themselves. No data to back that up on these specific parts, just a guess.

Bob

On Apr 17, 2012, at 7:28 AM, Bruce Griffiths wrote:

> Not yet, I just used the pair of TI evaluation boards which I obtained for another project.
> 
> I intend to mount the various components (splitters, 180 degree hybrids etc) on a thick aluminium plate to improve the mechanical and thermal stability of the system.
> 
> Bruce
> 
> Bob Camp wrote:
>> Hi
>> 
>> Did you do any temperature stabilization on the op amps?
>> 
>> Bob
>> 
>> On Apr 17, 2012, at 5:25 AM, Bruce Griffiths wrote:
>> 
>>   
>>> Subsequent measurements using an improved technique has allowed the true flicker phase noise characteristics of  a pair of OPA653 opamps to be determined.
>>> 
>>> Opamp
>>>    Gain 1x (6db folled by 6 db attenuator consisting of a 50 ohm resistor in series with the output of the opamp and the 50 ohm load resistor)
>>>    Signal input level: + 10dBm
>>> 
>>> OFFSET    Opamp PN (dBc/Hz)    Measurement system PN (dBc/Hz)
>>> 
>>> 1                -148                                -161
>>> 
>>> 10              -161                                -172
>>> 
>>> 100            -164                                -177
>>> 
>>> 1000          -164                                -179
>>> 
>>> Source: 10MHz low phase noise OCXO removed from a Thunderbolt amplified by a QBH9816 amplifier.
>>> 
>>> Conclusion: FET opamp PN in the flicker region can be quite low despite its somewhat higher baseband flicker noise than that of some bipolar input opamps.
>>> 
>>> Bruce
>>> 
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> 
> 
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