# Looking for documents about nodal analysis of opamps

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#### vickychand_2000

##### Junior Member level 2
Opamp Help

:? :? :? :? I am cannot understand the nodal anlysis of opamp as adder, subtractor,opamp as instrumrntation amplifier,comparator,rectifier,clipper etc.Can you give me some useful links or ebooks on these topics.

#### eda4you

##### Full Member level 5
Re: Opamp Help

I think it is best explained in Meyer&Gray 4th edition -->

Study chapter 8!

#### papyaki

Re: Opamp Help

Hi,

Opamp basic theory is only ohm's law. Have a look at this book from Texas Instruments :

h**p://homepage.mac.com/tbitson/weather/TI_OpAmp_Tutorial.pdf

* = t

#### ykishore

##### Member level 3
Re: Opamp Help

look! it seems that you are getting unnecessarily frightened with the simple op amp circuits.

It's all a matter of simple nodal / mesh analysis using simple rules that the input impedence of an op amp is infinite and the output impedence is zero.

Just use the above rules and apply the analysis methods.

That's it you will be able to solve the problems on opamps very easily

#### checkmate

Re: Opamp Help

If you know Ohm's Law, you can really calculate most of the op-amp equations, such as the gain. Just need the following 2 assumptions (for negative feedback configurations):-
1. The 2 terminals are a virtual short circuit, ie they are at the same potential
2. No current flows through the 2 terminals.

#### Kevin Weddle

Re: Opamp Help

An opamp has several charactersitics, but it is still a simple amplifier. This means it needs DC bias all the way around. The input transistors are low current which makes the impedance high. I believe that the feedback resistors are key to understanding gain. Just remember that it is a transistor built amplifier.

#### djalli

Opamp Help

Three things to remember for opamps:

1) Is a gain "Block" with ideally possessing infinite gain
2)Feedback.
3)There is a Network using lumped elements that sets the amount of feedback

As name suggest: opamp is a system/computer/machine call it whatever you like (built in IC in most of the cases) you can tweak the network (part 3) and do things with it.

Can you do with other elements? Yes of course you can do them using just transistors (BJT, FETs etc) and a lumped elements network. Can you do it? Hell yeah.

Wat op-amps simplify is that with simple tweaking of part (3) you can simplyfy a lot of things.

#### kidiotb

##### Member level 3
Opamp Help

Usually the Opamp circuits are analysed keeping the ideal characteristics of an oPAmp in mind.They are:
1.INfinite gain
2.Infinite input impedance
3.Infinite Bandwidth
4.ZEro Output Impedance
from the above characteristics we can put simply as:
No Current flows into or out of the input terminals
and also tat Both the input terminals will always be at same voltage level(negative feedback when applies reduces the differential input voltage to
Zero)

Keeping this in mind analyse the circuits ,simply removing the Opamp(forget it,but keep the voltages in mind).
Kareja.

#### dreamcard

##### Member level 2
Re: Opamp Help

kidiotb said:
Usually the Opamp circuits are analysed keeping the ideal characteristics of an oPAmp in mind.They are:
1.INfinite gain
2.Infinite input impedance
3.Infinite Bandwidth
4.ZEro Output Impedance
from the above characteristics we can put simply as:
No Current flows into or out of the input terminals
and also tat Both the input terminals will always be at same voltage level(negative feedback when applies reduces the differential input voltage to
Zero)

Keeping this in mind analyse the circuits ,simply removing the Opamp(forget it,but keep the voltages in mind).

just in ideal condition
Kareja.

#### dreamcard

##### Member level 2
Opamp Help

just in ideal condion

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