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How does this bandgap circuit work?

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eda_range

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bias question

Hi!
I am not sure but i think it is a reference bias.
Can anyone tell me how does it work? and what about its functions?
Thank you!
 

pankajdudulwar

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bias question

I suppose this is a bandgap reference start analyzing the circuit and u will find ur answer.If u are facing any problem revert back. I will try to help u out
 

eda_range

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bias question

thx,but can u tell me how this copy works here theoretically?
If this id a bandgap, there should be a resistor between Q3 and M13,but it doesn't. Why?

thank you !
 

waxtomato

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bias question

Typical Bandgap circuit, refer Razavi book
 

pfd001

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bias question

Sure it is bandgap reference. MO~M3 are for start up circuit.
 

zizu

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Re: bias question

eda_range said:
thx,but can u tell me how this copy works here theoretically?
If this id a bandgap, there should be a resistor between Q3 and M13,but it doesn't. Why?

thank you !
The resistor is between M8 and Q1. This is indeed the case because Q1 has 2 times of scale current than Q2. M0~M3 form the start up circuit and the remaining translate the bandgap reference voltage to the required bias voltage.
 

eda_range

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bias question

how does the start-up ckt work?
Here i know the W/L of M2,M3 is very small. if M1 conducts,the whole ckt starts to operate. But how does the M0,M2,M3 trigger M1 ?
And why put M14—M19 in this ckt?

Thank you in advance.
 

eda_range

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bias question

I still don't get it. If there is no resistor between M13 and Q3, this ckt is only a PTAT current generator and the output is a VT based ref not a bandgap.
Am I right?

Thank you!
 

zizu

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bias question

Assuming M4 is turned off, Vg4 will be closed to VDD and thus turn off M0 but turn M1 on.
When the circuit starts to operate and VB is no longer closed to VDD, Vg1 will be pulled up and M1 will be closed.
The size of M2 and M3 must be small enough to make sure M1 not conduct after the circuit starts to operate.
In my opinion, the right-hand-side circuit may be used to generate bias voltage for nmos current source via vg17 while not marked out.
M12-13-Q3 generate bias voltage for M6-7 not for bandgap ref.
I agree that this ckt is only a PTAT current generator with VB as its output.
This is not a complete BGR circuit but it will be BGR with little modification.
 

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