Bode plot performance of fully differential amplifier

[Junus2012]

Hello friends,

I am performing the bode plot of my fully differential amplifier,
I am using an oscilloscope with bode plot capability with its own local sine signal generator.

However, the sine generator is single ended, and I since I am interested in the plot at low frequency range, using the transformer balun will be a problem because in my search I see that all baluns are dedicated for RF range,

My testing range should be as low as possible (say 100 Hz) and upto 50 MHz.

So what I am doing for the moment, I connect one of the amplifier inputs at VCM and keep in the same time one output floating, so I am treating the fully-differential amplifier as single-ended input/output.

will this configuration give different value of f-3dB or phase as compared to fully-differential regular setup?

Of course the gain is dropping to the half expected from the fully differential one, but I am counting that in my graph

Thank you for your help in advance

Regards

 

[BigBoss]

If you do the calibration well, it will work.
There are many ICs around to convert the single ended to differential or vice-versa for low to mid frequencies.
Connect 2 of them back-to-back and do the calibration then insert your DUT between these two device.

 

[Junus2012]

If you do the calibration well, it will work.
There are many ICs around to convert the single ended to differential or vice-versa for low to mid frequencies.
Connect 2 of them back-to-back and do the calibration then insert your DUT between these two device.

Dear Boss,

Thank you for your suggestion, actually, my group leader is pushing me to avoid chaining of the analog amplifier as the way you mentioned, he wants a pure measurement of our chip,

But I didn't grab your point of making calibrating then it is well, can you please explain it me again

Regards