Oh. I'm sorry that where it is not virtual short in advance. It is Fully differential amplifier, not single ended output amplifier that couldn't make virtual short.
I observed PTAT CTAT node which is input voltages of fully differential amplifier. Actually to make virtual short, I think high open loop gain and negative feedback is essential. My folded cascode open loop gain is about 90dB at input range of upper 0.5V. So I think it's ok. But it wasn't virtual short. I think i am missing something to make this.