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

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grit_fire

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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!
 

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.
 
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?".
 
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 )
 
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