Applications of Op-Amp
OPERATIONAL AMPLIFIER or Op-Amp
An Operational Amplifier is a three-terminal device in which two terminals are input terminals and one terminal is an output terminal. One of the input terminals is shown by the ‘ + ’ sign, which is called a “Non-inverting Terminal”. And another one which is represented by the ‘ — ’ sign, is called an “Inverting Terminal”. As the name itself suggests, it is a device that does amplification. It takes a signal or a voltage as an input and gives amplified output. IC 741 is the most commonly used op-amp IC.
OP-AMP AS AN INVERTING AMPLIFIER
An operational amplifier circuit is connected to the feedback to produce the feedback operation in an inverting amplifier, which is a closed-loop circuit. There are two extremely crucial things to keep in mind while working with op amplifiers:
· No current goes to the input terminal and
· V1 and V2 are always equal (virtual ground).
I = (Vin — Vout) / (Ri + Rf)
Therefore, I = (Vin — V2) / Ri
I = (V2 — Vout) / Rf
The closed loop Gain is given as: A = Vout / Vin = -Rf / Ri
The closed loop voltage gain is : Vout = — (Rf / Ri)*Vin . .(1)
Here, V2 = voltage at inverting terminal.
The negative sign in the equation(1) indicates an inversion of the output signal respective to the input as its 180 degrees out of the phase.
OP-AMP AS A NON-INVERTING AMPLIFIER
A non-inverting amplifier with an output that is parallel to or in phase with the input In this circuit, the operational amplifier’s non-inverting input receives the signal. However, the feedback is sent from the output to the operational amplifier’s inverting input through a resistor, where it is then transferred to the ground by a second resistor.
The gain of the non-inverting amplifier circuit of the op-amp is easy to determine and the output of the non-inverting amplifier is the same as the input voltages. So, the gain of the amplifier is exceedingly high.
As the input to the op-amp draws no current this means that the current flowing in the resistors R1 and R2 and the voltage at both inputs is the same. The equation of the non-inverting amplifier can be shown as:
Vout / Vin = Av = 1+ R2 / R1
OP-AMP AS A VOLTAGE FOLLOWER
A voltage follower is an op-amp circuit with a voltage gain of 1. It is also known as a unity gain amplifier, a buffer amplifier, and an isolation amplifier. This indicates that the op-amp does not amplify the signal in any way. Because the output voltage matches the input voltage, it is referred to as a voltage follower.
A very high input impedance circuit is an op-amp. The usage of a voltage follower is due to this high input impedance. Large amounts of current are required and drawn by the load. As a result, the power sources draw enormous amounts of power. Another name for voltage follower is voltage buffer.
OP-AMP AS SUMMING AMPLIFIER
A summing amplifier is one of the applications for inverting operational amplifiers, but if we add an additional input resistor with values that are equivalent to those of the other input resistor, Rin, we end up with an addition op-amp that is known as a summing amplifier.
Also, it serves as a voltage adder circuit symbol in the summing amplifier input voltages V1, V2, and V3 and input resistors Rin and Rf. The summing applier is displayed in fig.6. So after applying KCL at X we get:
Vout = — Rf / Rin (V1 + V2 + V3)
So in general terms,
Vout = — Rf / Rin (V1 + V2 + V3 …)
OP-AMP AS A DIFFERENTIATOR
The output of an op-amp acting as a differentiator can equal the input signal’s first derivative. The relationship between the input signal and the output signal is shown in the following equation.
The charge on the capacitor equals Capacitance times Voltage across the capacitor:
Thus the rate of change of this charge is:
but dQ/dt is the capacitor current, i
OP-AMP AS AN INTEGRATOR
Op-amp is also utilised as an integrator. A signal’s amplitude and duration are both considered when determining the output of the integrator op-amp, which generates a signal that is proportional to both. We have a capacitor in place of a resistor in the feedback loop. As the output fluctuates with the input and signal duration, it may conduct the mathematical operation of integration.
Applying KCL, If = Iin
