operational amplifier internal circuitry

[vavachan]

i have read many books on operational amplifier and have studied some circuits in inverting and non-inverting configurattion...but i am not able to explain most of the circuits well...is it necessary to understand the internal circutry and the working of this to design and analyse op-amp involved circuits...

 

[kronos2k3]

Hi,

Not is necessary understand the internal circuit of Operational Amplifier to explain the diverse configurations.

You only need to understand the principles of operation. The operation principles are four:

-Input resistance infinite Ri=∞ (no input current)
-Output resitance zero Ro=0 (perfect source)
-Voltage gain infinite Av=∞
-Virtual short circuit V(+)=V(-)

With its four principles you can explain all circuits that involve operational amplifiers.

Example in inverting Amp:

The current that circulates through R1, is the same one that circulates around R2, because do not enter current in the amplifier.
Then, equaling the currents, its possible to find the gain.

The procedure is applied for the other circuits this way.

Regards from Argentina!

 

[diemilio]

One thing I think is important, is to know the operation limits of your opamp, like: output voltage saturation values, INPUT voltage saturation values, max and min Input and output currents, min input voltages, etc. Most of these specifications can be found in opamps' datasheets, but there are cases where SOME of these specs are not found, so there's where you need to try to understand the internal workings of your device.

I also think that if you have the time and pacience you should try to undestand how things work very down below, cause you never know when you're going to need that extra knowledge to solve other problems.

 

[rectifier]

It is not necessary to know about the internal ckt to analyze the op-amp containing circuits. But you should know the different modes of operation of opamps.