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

[Bruce Griffiths]

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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