information related opamp

Greeting every one.

I want to ask some basic question related to op amp.

1.Why gain of non-inverting amplifier will always be greater than 1?

2.Why output of inverting amplifier is 180 degree cut off phase from input?

kindly reply as soon as possible.

1: An op amp tries to make the -ve terminal voltage equal to the +ve terminal voltage.
If you tries to analyze the non-inverting amplifier you can see a potential diveder at
the output of the op amp to the ground via the -ve input terminal.
while the op amp try to make the input terminals equiv-potential, the output voltage should
be larger than the input voltage which then will get divided in the potential divider.
so the output voltage is now larger than the input voltage.
then output > input*1.(1 when multiplied with anything remains the same).
so output/input >1.
so the gain will always be greater than 1 for an non-inverting amplifier.

2: as i told in the above point that, the voltage at the two input terminal be equal (unless the op amp
goes to saturation), in a inverting amplifier the +ve terminal will be having zero potential with reference point as ground.
so to make the -ve terminal voltage as zero the op amp should create a signal with 180 degree phase shift so the voltage at the
-ve terminal will be equal to the +ve terminal voltage.

midhun raveendran said:

An op amp tries to make the -ve terminal voltage equal to the +ve terminal voltage.

Click to expand...

To be correct: It is not the opamp alone that "tries" to do this but it is the result of the feedback applied. To understand this effect one should try to become familiar with the concept of negative feedback.

thank you every one

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greeting every one

how can we differentiate between differential and instrumentation amplifier when input is 2Vp-p , 1kHz signal and gain is to be 3.

1: An op amp tries to make the -ve terminal voltage equal to the +ve terminal voltage.
If you tries to analyze the non-inverting amplifier you can see a potential diveder at
the output of the op amp to the ground via the -ve input terminal.
while the op amp try to make the input terminals equiv-potential, the output voltage should
be larger than the input voltage which then will get divided in the potential divider.
so the output voltage is now larger than the input voltage.
then output > input*1.(1 when multiplied with anything remains the same).
so output/input >1.
so the gain will always be greater than 1 for an non-inverting amplifier.

Click to expand...

What if one were to put an amplifier in the negative feedback path? So that if the op-amp outputs 1V, it will show as 2V on the input for example. Won't that give a gain less than 1?