[time-nuts] Fury Interface Board: How about TI OPA277?

[Bruce Griffiths]

David Forbes wrote:
> At 9:09 PM -0600 11/1/07, xaos at darksmile.net wrote:
>   
>> It is funny how things you forgot a long time ago have a way of coming back.
>>
>> Case in point. I was just running some simulations on the EFC
>> interface and then I had this idea.
>>
>> Wouldn't an instrumentation amplifier be the right way the isolate the
>> Fury EFC    voltage?
>>
>> For instance, the Burr Brown INA 103. It would provide for isolation
>> as well as gain. Not sure of all the details yet.
>>
>> I remember using this device for a thermocouple a few years back. And
>> I even managed to find a few of them in a box somewhere.
>>     
>
> The AD620 or LT1167 is a fine little instrumentation amp. 8-pin 
> package. Very easy to use, good specs.
>
>
>   
AD620 is quite noisy at low gains as is the LT1167.
For this application with a 5V EFC range from the Fury a gain of 2X is
all thats required for an HP10811A.
For a 20V (-10V to +10V) output EFC swing a gain of 4 is sufficient.
Since these devices use an external gain setting resistor, gain tempco
may be higher than desired.
Using the 10811A(or 10544A/B) EFC ground pin to remotely sense the
ground on the circuit board will minimise the effect of voltage drops
across the 10811 connector.
>> There is no question that he TL431 is not right here. I am already
>> running the simulation with an LM128 or such. PSPICE only has the
>> LM128 so I am just testing this out.
>>
>> -George
>>     
>
> The REF19x series is very good at this sort of job. Also 8 pins.
>
>   
These are relatively noisy devices.

Bruce