What is an Operational Amplifier
AN operational amplifier is a high-gain electronic voltage amplifier that is used in analog and mixed-signal circuit designs. It amplifies the voltage difference between the inverting and the non-inverting terminals.
It is very useful for signal conditioning, filtering, and mathematical operations like addition, subtraction, integration, and differentiation. Op-amps’ high input impedance and low output impedance enable efficient signal transfer, which is useful in applications like sensor signal amplification, analog-to-digital conversion circuits, active filters, voltage followers, and control systems.
Operational Amplifier Symbol
AN op-amp symbol is typically represented in a triangular shape pointing towards the right, which symbolizes the direction of signal flow from input to output. It has two input terminals at the base of the triangle, i.e., the inverting input (-) and the non-inverting input (+), and one output terminal at the tip of the triangle.
The inverting input produces a 180-degree phase shift, and the non-inverting input shows that it maintains the input signal’s phase.
Types of Amplifier
1.Voltage Amplifier
This Op-amp amplifies the voltage difference between the inverting and non-inverting inputs and gives a high voltage gain with very high input impedance and low output impedance. It is used in audio amplifiers, signal conditioning, and sensor interfaces.
2.Current Amplifier
Current op-amp converts the small input current into a larger output current and maintains a constant voltage while boosting current. It is used in current sensing, low impedance loads, and driving LEDs or motors.
3.Differential Amplifier
This type of amplifier has high common-mode noise rejection, which is used to amplify the difference between two input signals. They are used in sensor interfaces, instrumentation, and op-amp input stages.
4. Inverting Amplifier
This type of op-amp produces an output that is inverted ( 180 degrees out of phase) relative to the input and has a simple gain just by using two resistors. It is used in signal inversion, active filters, and phase shifters.
5. Non-Inverting Amplifier
Non-inverting amplifier has a very high input impedance, and the gain is easily set by a resistor network. Its output is an amplified signal that is in phase with the input. It is mainly used in buffers, voltage followers, and sensor signal amplification.
6. Differentiator Amplifier
This type of amplifier has high common-mode noise rejection, which is used to amplify the difference between two input signals. They are used in sensor interfaces, instrumentation, and op-amp input stages.
7. Instrumentation Amplifier
Instrumentation Amplifier precisely amplifies low-level differential signals while rejecting common-mode noise. It has a high input impedance, adjustable gain, and has good common-mode rejection ratio. This is used in medical devices (ECG, EEG), industrial measurement, data acquisition systems, etc.
8. Integrator Amplifier
Integrator op-amp provides an output voltage proportional to the integral of the input signal over time and uses a capacitor in the feedback loop. This is used in analog computers, ramp signal generators, active filters, and signal processing.
9. Comparator
Comparator operates in open-loop mode to compare two input voltages and switch the output to high or low, and it acts like a 1-bit ADC. It is used in zero-crossing detectors, voltage level detection, and PWM circuits.
10. Precision op-amps
Precision op-amps are designed for high accuracy with minimal offset voltage and low bias current. It is used in measurement instruments, reference circuits, and accurate signal conditioning.
11. High speed Op-Amps
High-speed Op-amps deliver fast slew rates and high gain-bandwidth product, and they support wide frequency response. It is used in video signal processing, RF circuits, and fast data acquisition.
12. Low Power Op-Amps
Low-power op-amps consume minimal power while providing essential amplification. This op-amp is optimized for battery-operated and portable devices and is used in IoT devices, wearables, remote sensors, and wireless modules.
Working Principle of an Operational Amplifier
An operational amplifier works by amplifying the voltage difference between its inverting (-) and non-inverting (+) inputs.
When there is a small differential input voltage is applied, the op-amp’s internal differential amplifier stage senses the difference.
The differential amplifier feeds its output to an internal gain stage, which boosts the signal by a very large open-loop gain, typically 10,000 to 1,000,000 times.
Negative feedback is usually applied externally through resistors or capacitors to control and stabilize the gain.
Due to negative feedback, the op-amp automatically adjusts its output so that the voltage difference between the inverting and non-inverting inputs becomes nearly zero.
This self-balancing action allows the op-amp to maintain a linear output response for varying input conditions.
The output voltage is proportional to the difference between the inputs multiplied by the closed-loop gain determined by the external feedback network.
The power supply rails connected to the op-amp provide the necessary energy for amplification, but do not affect the input signal directly.
Because of high input impedance, the op-amp draws minimal current from the input source, ensuring accurate signal processing.
The low output impedance allows the op-amp to deliver significant current to the load without significant voltage drop.
This working principle makes the operational amplifier ideal for applications like amplification, filtering, integration, differentiation, and analog computation.
Applications of Operational Amplifiers
1. Operational amplifier is used as a voltage amplifier in audio, sensor, and instrumentation circuits to boost weak signals.
2. For filtering, amplifying, and modifying input signals for ADCs and microcontrollers, an op-amp is used as a signal conditioner.
3. For precise frequency selection op-amp is used in active filters (low pass, high pass, band pass, and band stop).
4. Op-amps are essential in comparator circuits for voltage level detection, zero-crossing detection, and pulse generation.
Frequently Asked Questions
1.What is the function of an operational amplifier?
The function of an operational amplifier is to amplify the voltage difference between its inverting and non-inverting inputs.
2. What are the 3 main characteristics of an op-amp?
The three main characteristics of an op-amp are high input impedance, low output impedance, and very high open-loop voltage gain.
3.What is the difference between an inverting and non-inverting op-amp?
An inverting op-amp produces an output that is 180 degrees out of phase with the input, while a non-inverting op-amp outputs a signal that is in phase with the input.
4. Can an op-amp be used as a comparator?
Yes, an op-amp can be used as a comparator by operating it in open-loop mode to compare two input voltages.
5.Why is feedback used in op-amp circuits?
Feedback is used in op-amp circuits to control gain, stabilize the output, and improve accuracy and bandwidth
