Design of differential amplifier (NMOS) using Current Mirror (NMOS)

[skywalkerluk]

Hello eveyrone,

I would like to design a differential amplifier with passive resistor load, using the current mirror or a single NMOS as my constant current source. The figure is attached. I know that the transistor below node A should be biased in saturation in a current mirror. However, the simulated voltage at node A is very low and the transistor does not remain in saturation. In textbook or online exanple, a standalone current mirror has both drains of the two NMOS connected to Vdd (both in saturation), so this problem does not occur. How do I resolve this problem when I incorporate the current mirror into a differential amplifier shown in the figure? Thank you very much.

 

[naveensai12]

What is the DC voltage input level of the Diffamp.It should be more than Vgs from the ground.So you can go with 1v as the DC level of the input signal

 

[analog_curious]

there should be a DC level given at the inputs of the differential amplifier
ideally, current mirror work as expected only when the Vds of both the current mirror transistors are equal.
Also make sure that you have the expected current out of the current mirror for the chosen transistor widths of the current mirror

Dan