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Current Mirror biasing

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Ipanema

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Guys,

Pls help to comment on these 5 types of current mirror reference generator biasing circuit shown in the attachment. Which one is most suitable for biasing differential amplifier tail? Figure of merit e.g. Constant gain across process and temperature variation, low input offset voltage for comparator etc.

Pls show me if there is other better biasing circuit.

Thanks.
 

accordin to me bandgap current biasing is the best.... as it is immune to temperature variation and the other things that you have mentioned can be achieved using it....
 

Thanks for your comment. Do you think that it is neccesary to bias all opamp with Bangap current?

What do you think of PTAT biasing? It seems to be compensating for input gm variation across temperature.

Biasing 1, 2 and 3 are more commonly use for biasing. Which one do you think is better? Why?

Thanks.
 

Ipanema said:
Thanks for your comment. Do you think that it is neccesary to bias all opamp with Bangap current?

What do you think of PTAT biasing? It seems to be compensating for input gm variation across temperature.

Biasing 1, 2 and 3 are more commonly use for biasing. Which one do you think is better? Why?

Thanks.
Click to expand...

I agree. sometimes We need PTAT bias current to compensate the high temp characteristic of opamp. But if your circuit need temp stable character, I think the bandgap biasing is good.

So, I think which type of biasing is to be used should rely on your requirement.
 

Guys,

Just want to do a quick survey on this :

Which one of the biasing that you use most often? and in which circuit?

Thanks,
 

Ipanema said:
Guys,

Just want to do a quick survey on this :

Which one of the biasing that you use most often? and in which circuit?

Thanks,
Click to expand...

I think you haven't clearly recognize it.

as a current reference, you should use low TC current(bandgap current).

as in other condition, PTAT or bandgap's current will both be ok.

but if you want to get a result, maybe bandgap's current is used often, as I know.
 

Can you point me to some bandgap reference current generator for biasing? I only have bandgap voltage generator (Brokaw), but using I/V converter to generate bandgap current this way will produce error because of resistor tolerance.

Thanks.
 

I am sorry I didn't have bandgap current biasing docs to help you.

I usually generate current through current reference not bandgap.

so you have to find it yourself. sorry.
 

Bias1,2,3 rarely find usage for current bias according to big variation as VDD changing, temperature variation and process fluctuation. VDD changing is the more serious one among them. Vgs2+Vgsn=VDD. And Id is related to (Vgs-Vth)^2. However, they might still be used in some case that bias is required to be depended on VDD.
 

The type of tail curent varies among circuits for some circuits ou may need bandgap for other you may use constant gm biasing (see Razavi's book).

how ever I hope following two papers can help u.
 

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