LDO input-output characteristic problem

[hanhan]

Hi.
Please help me solve the problem with my LDO in the picture below. Thank you.

 

[ronsimpson]

I need more information.
Part numbers.
What is Vbg? How is this voltage made?
Power supply pins on op-amp?
Resistor values?
Where are the capacitors?
Load current?

 

[hanhan]

Thank you.
I simulated the circuit in Cadence using TSMC 180nm.

What is Vbg? How is this voltage made?

I used a bangap circuit with Vbg = 0.8V.
It is relatively good.

Power supply pins on op-amp?

Opamp is powered from Vin (2 to 3.3V)

Resistor values?

Top resistor: 100K
Bottom resistor: 80K.

Where are the capacitors?

Cload = 1pF.

Load current?

I didn't measure it. But Rload = 180Ohms and therefore, Iload = 0.01A.

 

[ronsimpson]

So the op-amp is powered from Vdd, the same as on the source of the MOSFET.
What op-amp are you using? I need to know input range. If you give a part number I can find the numbers I am looking for.
What MOSFET are you using? I need to know gate turn on voltage. N or P?
Please plot Vdd and Vout, Gate of MOSFET. I want to see the output of the opamp.