Comparison of folded and telescopic cascode opamp

[surianova]

folded cascode opamp

Hi all,

What is the advantage of folded cascode opamp compare to telecospic
cascode opamp and olso its application? Thanks in advanvce.

 

[eda4you]

Re: folded cascode opamp

Hi all,

What is the advantage of folded cascode opamp compare to telecospic
cascode opamp and olso its application? Thanks in advanvce.

Hi,

the big advantage of a folded cascode is its larger outputswing. And as you know the more signal range, the higher the SNR. Unfortunately you have more branches between Vdd and Vss, and therefore the folded cascode dissipates more power. However, as Vdd decreases more and more, telescopic opamps will more and more dissapear.

If you use not a 2nd stage, this opamps are otas and are used in SC design for instance.

 

[JiL0]

folded cascode opamp

Can i say that an amp is a OTA if its output resistance is high and it is an OPAMP when the output resistance is low?

 

[eda4you]

Re: folded cascode opamp

Can i say that an amp is a OTA if its output resistance is high and it is an OPAMP when the output resistance is low?

In my mind it is right.

___________in_________out_______ideal output resistance___characteristic equ.

OTA --> ___ voltage ___current____ oo (very very high) ___transconductace (Iout=Gm*Vin)

opamp --> ___ voltage ___ voltage ___ 0 (very very low) ___ voltage gain (Vout=A*Vin)



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[ablue]

folded cascode opamp

When Vdd decreases , telescopic hasnt enough voltage room for large output swing and folded cascode may still can . Besides, folded cascode has large input range than telescopic

but folded cascode dissipates more power because of more branch, and also folded cascode are slower than telescopic because of more parasitic capacitance at the folded node

 

[fashion]

folded cascode opamp

The advantage of Folded cascode is wide output swing then telescope.

 

[anadigi]

Re: folded cascode opamp

swing is the advantage..
power and speed is the disadvantage..
refer razavi for more detailed analysis.