[SOLVED] Is it okay to float the negative output of a differential amplifier?

[grit_fire]

Hi, all,

I have a LPF whose output is differential, and I am connecting it to the next stage which is a single-ended input power amplifier. I wonder if it will cause any problem is I only connect the positive output from the LPF to the PA and leave the negative output floating?

Thank you!

 

[vishak]

It can be done as long as you keep the length of the unused output trace to a minimum in order to minimize capacitance and
potential noise coupling.

 

[dick_freebird]

I would say that for symmetry's sake you'd like to terminate
it to an equivalent voltage and impedance, especially if there
is an internal common-mode feedback scheme. Otherwise your
output common mode might be the average of the + output
and "WTF?".

 

[gasingh]

You are surely going to loose some benefits of Differential Output ,

1- PSSR will be bad because the DC part output ( which is now a signal instead of output CM ) will change with fluctuation in current source of I/2 due to supply noise
2- The CMRR will also be effected to a lesser extent because the resistance of input MOS is changing with input common mode voltage and this will slightly change the output common mode ( due to non ideality current source load )