What wrong with my two stage OpAmp design ?

Question

Hello all, I'm designing a DAC circuit, and I stuck at designed a 2 stage OpAmp from transistors, I followed the instructions from book CMOS Analog Circuit Design. And finally, my simulation not as expect (the red line), output signal which is < 0.4V cannot be amplifier. What aspect should I consider if the output voltage like image ? 
 Thanks all in advance.

MarkThoren · Answer

Hi anaen1310200 , 
 What are the inputs tied to? Are they floating? Try putting the amplifier in a simple closed-loop configuration, like a voltage follower, gain of +2, gain of -1, etc. with an appropriate input signal - simple sinewave, square wave, etc., something that will let you at least see that the circuit is operating at all. 
 Note that you may need to bias the input source, or add a DC offset, in order to meet the common-mode voltage requirements of the inputs. 
 -Mark