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What is an error amplifier and how to design it?

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Chethan

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what is error amplifier

Hi,
can some one provide me materials or links of what is an error amplifier and how to design an error amplifier. How is an error amplifier different than a differential amplifier.
Thanx in advance
 

paulux

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Re: what is error amplifier

There are many types of amplifiers, such as high gain, low bandwidth and vice versa, voltage/current mode.
Error amplifier is just a name of a amplifier that usually compare the difference between two signal. Therefore its main characteristic is the gain of the amplifier because the larger the gain, the small the error it can compare. Certainly other requirement such as bandwidth or slew rate depends on the system requirement. Hope this help
 

johnsmith101

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Re: what is error amplifier

In addition to the above stated, low offset is another important parameter of an error amplifier, since the accuracy of the system is often dictated by this.

What application are you using this amplifier for?
 

Chethan

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Re: what is error amplifier

johnsmith101 said:
In addition to the above stated, low offset is another important parameter of an error amplifier, since the accuracy of the system is often dictated by this.

What application are you using this amplifier for?

I have to design an LDO with an Error amplifier in it
 

johnsmith101

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Re: what is error amplifier

Depending on your requirements, you could use a simple Nchannel input two stage buffer as an LDO.
 

sudheer_vlsi

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Re: what is error amplifier

Hi,

If u r designing the error amplifier for LDO,see to it that it has low output impedence.high output impedence may result in dominant pole and may create problem in stabilization.hence its better to keep buffer at the output of the error amplifeir so that it splits the poles into two high frequency poles.
 

jutek

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Re: what is error amplifier

sudheer_vlsi said:
Hi,

If u r designing the error amplifier for LDO,see to it that it has low output impedence.high output impedence may result in dominant pole and may create problem in stabilization.

it depends on queisecent current. low output impedance means much more current

regards
 

jinxingsun

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what is error amplifier

In many products of voltage regulator and LDO,you can find the error amp.
 

rekha410

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Re: what is error amplifier

depending upon requirement design error amplifier .if u want to improve the regulation charcteristics increase the gain of the amp by using 2 or 3 stage amplifier..but u have to make sure that system must be stable ...
 

hung_wai_ming@hotmail.com

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what is error amplifier

Error amplifier is its name implies, to amplify the errors from the two inputs. Since this kind of amplifier usually employed in some negative feedback system to keep track the input voltage difference between +ve and -ve inputs like in LDO, DC-DC converter, V to I converter.
Basically, it is just an OTA with specifications you defined, say gain, bandwidth and offset.
 

rfzheng

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what is error amplifier

maybe you should read allen's book, it has detailed information about ampifier
 

viperpaki007

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Hi, what is the difference then between error amplifier and a comparator then. Comparator output is also equal to difference of input voltages multiplied by the large gain
 

anhnha

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Re: what is error amplifier

Hi,

If u r designing the error amplifier for LDO,see to it that it has low output impedence.high output impedence may result in dominant pole and may create problem in stabilization.hence its better to keep buffer at the output of the error amplifeir so that it splits the poles into two high frequency poles.
Please, could someone explain it in detail? I am interested why we need the buffer here. Any link or explanation would be much appreciated.
Thanks.
 

Audioguru

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Hi, what is the difference then between error amplifier and a comparator then. Comparator output is also equal to difference of input voltages multiplied by the large gain
The output of a comparator switches high and low. The voltage gain of a comparator is as high as is possible, no negative feedback is used.
The output of an error amplifier in a voltage regulator is linear. An error amplifier usually uses negative feedback.
 

dick_freebird

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Error amp is an -application- of a differential amplifier.
An op amp is a good conceptual starting point. You may
however (and likely) want to not make the error amp
"ideal" - for example you may not want near-zero output
impedance, if you need to override the amplifier output
for soft start or just the ability to compensate the loop
by a pin-attached shunt capacitor; the amplifier is not
a general purpose piece, but role-optimized.

Because there will be much, but probably also very variable
downstream gain within the loop, the error amp may be
uncompensated or differently compensated than you would
for a general purpose piece-part. You also may not need
things like true rail-rail input or output depending on the
reference voltage (at 0.6V VRef, input range had better
be real close to ground; at 5V Vref, you have plenty of
headroom for a simple classical op amp (as long as you're
sure it won't go into front end cutoff or phase inversion).

So you have some added liberties, and you have some
added demands (esp. the output's interfacing with the
rest of the control loop).
 
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