What are the advantages of current mirror OTA ?

[quaternion]

What are the advantages of current mirror OTA ?
Could it be considered a good topology for LDO error amplifier -at least as a first stage-(I have saw it in some papers but without reasoning for its usage)?
What I know is that it has a larger output swing & 1 pole-& the other is at high frequencies- (although composed of 2 stages).Also, it can be fully differential without the need for common mode feed back.
I need confirmation about these.
What are its disadvantage ?
Any recommended papers or .. .

 

[kennyg]

current mirror ota gain boost

The gain of the current mirror OTA is low.This is the biggest disadvantage.

 

[quaternion]

cmos ota

But What I know is that the second stage (whose input is mirrored by a current from the input stage ) could have a gain like that of normal 1stage OTA , in addition to the mirroring ratio which may boost the gain a little !?

 

[kennyg]

Current mirror OTA

a paper ("A 0.8V 8-uw,CMOS OTA with 50-dB gain
and 1.2-Mhz GBW in 18-pF load") fullfill your needs.
Authors:Libin Yao,Willy Sansen.

 

[rosaeidi]

Current mirror OTA

Hi

Current mirror circuits have high frequency, low voltage, low power and easily implementation performances.

 

[quaternion]

Re: Current mirror OTA

What about the gain and stability in closed loop circuits as LDO?

In the Millikan paper "Full on chip CMOS LDO",He had used current mirror OTA ,what are the advantages he gained from this?

He has added nmos transistors below the pmos transistors in the second stage in order to adjust the inaccuracies and mismatches that are magnified by the disturbance added by the compensation circuitry ,How does this affect the performance of the current mirror OTA & how does this result in a better DC offset immunity?

 

[forkschgrad]

Re: Current mirror OTA

What about the gain and stability in closed loop circuits as LDO?

In the Millikan paper "Full on chip CMOS LDO",He had used current mirror OTA ,what are the advantages he gained from this?

He has added nmos transistors below the pmos transistors in the second stage in order to adjust the inaccuracies and mismatches that are magnified by the disturbance added by the compensation circuitry ,How does this affect the performance of the current mirror OTA & how does this result in a better DC offset immunity?

do u have a copy of this paper? tnx.

 

[quaternion]

Re: Current mirror OTA

It is here in the forum.

 

[RFDE]

Re: Current mirror OTA

The main advantage of the current mirror OTA is its GBW which is higher than other OTA's configuration like folded,cacode & two stage , yet , this comes on the expense of lower gain than the conventional 2 stage OTA , so, it is used in applications requiring high BW

 

[s_babayan]

Re: Current mirror OTA

Dear Friends

In a paper I studied that since current-mirror OTA has small-node impedancxe, the poles are so large so that a fully-differential current-mirror OTA doesn't need Compensation scheme, so as it consumes a lot of power and area in compare with conventional OTA. Good luck

 

[quaternion]

Re: Current mirror OTA

Dear Friends

In a paper I studied that since current-mirror OTA has small-node impedancxe, the poles are so large so that a fully-differential current-mirror OTA doesn't need Compensation scheme, so as it consumes a lot of power and area in compare with conventional OTA. Good luck

What is the name of this paper ?

 

[s_babayan]

Re: Current mirror OTA

Thanks,

Here is the name of the paper I told you about:

[1]. A 0.8-V 0.25-mW Current-Mirror OTA With 160-MHz GBW in 0.18- m CMOS

Good Luck

 

[safwatonline]

Re: Current mirror OTA

What are the advantages of current mirror OTA ?
Could it be considered a good topology for LDO error amplifier -at least as a first stage-(I have saw it in some papers but without reasoning for its usage)?
What I know is that it has a larger output swing & 1 pole-& the other is at high frequencies- (although composed of 2 stages).Also, it can be fully differential without the need for common mode feed back.
I need confirmation about these.
What are its disadvantage ?
Any recommended papers or .. .

i doubt that.

 

[quaternion]

Re: Current mirror OTA

Thanks s_babayan.

Also, it can be fully differential without the need for common mode feed back.
I need confirmation about these.

i doubt that.

I think for the 1st stage alone that holds(whenever the ICMR is in a certain range) , while for for the second stage I am not sure .

 

[safwatonline]

Re: Current mirror OTA

Also, it can be fully differential without the need for common mode feed back.
I need confirmation about these.

i doubt that.

I think for the 1st stage alone that holds(whenever the ICMR is in a certain range) , while for for the second stage I am not sure .

yep, the first stage is diode connected loaded (low impedance) but the second u will need CMFB cause of the high impedance at the output.

 

[quaternion]

Re: Current mirror OTA

He has added nmos transistors below the pmos transistors in the second stage in order to adjust the inaccuracies and mismatches that are magnified by the disturbance added by the compensation circuitry ,How does this affect the performance of the current mirror OTA & how does this result in a better DC offset immunity?

I forgot that we have discussed that circuit before. :|



But there its source (Dr Millikan paper) wasn't mentioned.