Differential amplifier

Hello,

In short, a differential amplifier has a differential input & single-ended output. Output = input differential * gain. You can find more details here:

Difference Amplifier circuit

Instrumentation Amplifier Video Series

For Fully differential amplifiers, both the inputs and outputs of the device are differential. Output differential = input differential * Gain. You can find more details here:

Fully Differential Amplifier Video Series

Best,

Hasan Babiker

And incidentally, that common mode loop actually allows a new (kind of breakthrough) solution that was hiding inside all FDA's undiscovered for quite some time - I pounded through the required equations while at Intersil and published in these two articles - if you need matched input impedance single to differential, what is described gives you the lowest noise solution using what I call an Active Balun solution. I did a series of videos on these as well if you are interested. 

https://www.edn.com/wideband-matched-input-impedance-with-ultra-low-noise-using-the-active-match-capability-of-a-new-type-of-amplifier-part-1-of-2/

https://www.edn.com/wideband-matched-input-z-using-active-match-and-a-new-type-of-amplifier-part-two-of-two/