Dear ULPAnalog,
Thank you for your directive answer. It helps a lot.
The circuit is bias well now. I use resistors as you depict
them in your figure. Those resistors biased the gate of the input
transistor as vocm.
Now, I would like to eliminate the tail current as depicted
in the figure in this message. However, it is hard to guarantee
the current flowing on each branch, and biasing with resistors
in the same topology does not help. Since the gates of the input
transistors are not set to vocm.
Dear ULPAnalog, I hope you would like to enlighten how
to bias a tailless pseudo differential amplifier
Thank you in advance
Regards