BOOK NAME: Microelectronics Circuits
Author: Sedra Smith
Summary:
From a signal point of view the op amp has three terminals: two input
terminals and one output terminal. Terminals 1 and 2 are input
terminals, and terminal 3 is the output terminal. Two terminals, 4
and 5, are brought out of the op-amp package and connected to a
positive voltage VCC and a negative voltage −VEE, respectively.No
terminal of the op-amp package is physically connected to ground.
Characteristics of OPAMP:
1. Infinite input impedance
2. Zero output impedance
3. Zero common-mode gain or, equivalently, infinite common-mode
rejection
4. Infinite open-loop gain A
5. Infinite bandwidth
Inverting OMAMP Configuration:
Inverting OMAMP consists of one op amp and two resistors R1 and R2.
Resistor R2 is connected from the output terminal of the op amp,
terminal 3, back to the inverting or negative input terminal,terminal
1.if R2 were connected between terminals 3 and 2 we would have called
this positive feedback.Thus the voltage vO will not depend on the
value of the current that might be supplied to a load impedance
connected between terminal 3 and ground.
The Closed Loop Gain:
The gain A is very large (ideally infinite). If we assume
that the circuit is “working” and producing a finite output voltage
at terminal 3, then the voltage between the op-amp input terminals
should be negligibly small and ideally zero.Voltage at the inverting
input terminal (v1) is given by v1 = v2.
A virtual short circuit means that whatever voltage is at 2 will
automatically appear at 1 because of the infinite gain A.
A virtual ground is, having zero voltage but not physically connected
to ground.