fully differential buffer?

[blue2lucy]

For a fully dif op amp, aka 2 inputs and 2 outputs, apparently we can't directly connect the inputs and outputs (with opposite palarity) together to form a buffer. Then what is the best way to impement a fully differential buffer? What I can think of is resistor feedback configuration with gain of 1 or switched-cap...

 

[IanP]

Have a look at the configuration of the NE592 differential amplifier:
https://www.onsemi.com/pub/Collateral/NE592-D.PDF
With couple of external resistors the gain can be adjust to 1, so you will have fully differential buffer.
Regards,
IanP

 

[blue2lucy]

Thank you. That's also what I've done before. But that's not a good buffer - the input resistance actully lower than that of the single ended version (non-inverting).