Hi, all
I don't know how to simulate whether the bandgap circuit is stable. I use such a way as the figure. I use a small step signal V. Then I run transient to see whether the output is stable. Does that method right? Why? Can someone tell me how to simulate whether the BGR is stable?
I will appreciate for your reply!
Thank you in advance!
Hi gte582w,
You said my measure is right and I also need to add step signal at two inputs and supply. But someone said I should AC simulation which I am not good at. I am misunderstanding which method is right.
Can somebody explain?
you should simulate the AC. Break the loop the input of the amplifer, put the ac input signal to the input of the amplifier, then you can get the phase margin at the e of the Q1
Hi pfd001,
I have done as you said. But the gain is negative, the phase decrease from 0 degree. I don't know how much the phase margin is. I want to ask another question. You said I should put the ac input signal to the negative input of the amplifier. Can I put the ac signal at the positive input?
you will use stb to do AC check of the loop gain and phase margin,
but remember AC is small signal, therefore, I would trust ultimately
the transient, that is why step the inputs and supply lines are must.
Hi pfd001,
I have done as you said. But the gain is negative, the phase decrease from 0 degree. I don't know how much the phase margin is. I want to ask another question. You said I should put the ac input signal to the negative input of the amplifier. Can I put the ac signal at the positive input?
It must be sth wrong. If it is true, your bandgap can't work. You put the differential signal at the positive and negative input. you can simulate it just like you did for amplifier
As i know, i will do two simulations about the stable problem of the bgr.
first i will give a setp power and do the tran simulation of the circuit, then you will find the circuit is stable or not and wether it can work properly.
Second i will add AC signa on the power suplly and do the ac simulation, you will get the psrr and bandwidth of the bgr, these give you a reference.
lics said:
Hi, all
I don't know how to simulate whether the bandgap circuit is stable. I use such a way as the figure. I use a small step signal V. Then I run transient to see whether the output is stable. Does that method right? Why? Can someone tell me how to simulate whether the BGR is stable?
I will appreciate for your reply!
Thank you in advance!
you can refer to hurst's paper about loop gain or return ratio simulation. you can refer to the ook--<<the designer's guide to spice and spectre>> also