- Op Amp Definition: An operational amplifier (op amp) is defined as a linear amplifier with high gain, high input impedance, and low output impedance.
- Inverting Amplifier: Op amps can be used as inverting amplifiers to provide a stable, linear relationship between input and output.
- Non-Inverting Amplifier: Op amps as non-inverting amplifiers offer high input impedance and adaptable voltage gain without phase inversion.
- Summing Amplifier: Op amps can sum input voltages from multiple sources into a single output voltage, useful for combining signals.
- Applications of Op Amp: Op amps are used in various applications including phase shifters, scale changers, differentiators, and voltage comparators.
A linear amplifier like an op amp has many different applications. It has a high open loop gain, high input impedance and low output impedance. It has high common mode rejection ratio. Due to these favourable characteristics, it is used for different application. In this article, we are discussing some of the most prominent uses of an Op amp. This is not an exhaustive list but covers the important applications of op amp within the scope of our discussion.
Op Amp applications as Inverting Amplifiers
Op-Amp can be used as an inverting amplifier.
- The inverting circuits, implemented with an Op-Amp, are more constant, distortion is comparatively lower, provide a better transitory response.
- When Op-Amp is applied in a closed loop, there is a linear relationship between input and output.
- The inverting amplifier can be applied for unity gain if Rf = Ri (where, Rf is the feedback resistor and Ri is input resistor)
Op Amp Applications as Non Inverting Amplifiers
When the input signal is applied to the non-inverting input (+), the output is fed back to the input through a feedback circuit made up of Rf (feedback resistor) and Ri (input resistance).
- Voltage gain without any kind of phase inversion. In transistor equivalent, there are minimum 2 transistor stages needed to do this.
- High input impedance compared to Inverting input.
- Easily adaptable voltage gain.
- The total remoteness of the signal supply from the output.
Op Amp application as a Phase Shifter
Op-Amp is used in direct coupling, causing the DC voltage level at the emitter terminal to increase with each phase. This rise can shift the operating point of the next stages. A phase shifter adds a DC voltage level to lower this swing, bringing the output back to ground level.
Op Amp as Scale Changer
Op-Amp functions as a scale changer through small signals with constant-gain in both inverting and non-inverting amplifiers.
Non-inverting terminal is grounded whereas R1 links the input signal v1 to the inverting input. A feedback resistor Rf is then connected from output to the inverting input. The closed loop gain of the inverting amplifier works based on the ratio of the two external resistors R1 and Rf and Op-Amp acts as a negative scaler when it multiplies the input by a negative constant factor.
While in need for an output that is equal to input for getting multiplied by a positive constant the positive scaler circuit is used by applying negative feedback.
Op Amp Applications as Adder or Summing Amplifier
Op-amp can be used to sum the input voltage of two or more sources into a single output voltage. Below is a circuit diagram depicting the application of an op-amp as an adder or summing amplifier. The input voltages are applied to the inverting terminal of the op-amp. The inverting terminal is grounded. The output voltage is proportional to the sum of the input voltages.
Op Amp Applications as a Differential Amplifier
Differential Amplifier is a useful blend of both the inverting amplifier and non-inverting amplifier. It is mostly used to amplify the diversity amid two input signals.
Major applications of Differential Amplifiers are
- Signal Amplification
- Input stage emitter coupled logic
- Switch
- Controlling of Motors and Servo Motors
Example: it is useful while eliminating the noise in ambience as through differential amplifier, you can eliminate the connected protected cable or twisted pair cable mostly used to eradicate the transitory noise.
Op Amp application as a Differentiator
An op-amp can act as a differentiator, producing an output that is the first derivative of the input signal. This relationship is defined by a specific equation.
As you can see the output voltage is a first derivative of the input voltage. We are not going into how the equation is derived but only learning about the use of an op amp as a differentiator.
Op Amp Applications as Integrator
Op-amp is used as an integrator also. The integrator op-amp produces an output that is proportional to the amplitude of the input signal as well as the duration of the input signal. Instead of a resistor in the feedback loop, we have a capacitor. It is able to perform the mathematical operation of integration as the output varies with the input and duration of the signal.
Op Amp Applications as Voltage to Current Converter
An op amp with negative feedback is used for voltage to current conversions. In the circuit, the voltage is applied to the non-inverting terminal, and the output is fed back to the inverting terminal. A resistor is used to ground the circuit.
Op Amp Applications as Current to Voltage Converter
Op-amp can be used as a current to voltage converter using a very simple circuit as shown above. All we need is a feedback resistance connected to the output of the op-amp. The current source is fed into the inverting terminal and the non-inverting terminal is grounded. Here the output voltage is proportional to the input current. As an ideal op-amp has infinite resistance, the current cannot flow through the op-amp. The current flows through the feedback resistance and the voltage across it depends on the current source.
Op Amp Applications as Logarithmic Amplifier
The logarithmic amplifier using op-amp is made by using a diode instead of a resistance in the feedback loop. The non-inverting terminal is grounded and the input voltage is fed to the inverting terminal. The output voltage is proportional to the logarithm of the input voltage and hence can be used as a logarithmic amplifier.
Op Amp Applications as Half Wave Rectifier
The circuit diagram above shows the usage of an op-amp as a half wave rectifier. During the positive cycle of voltage, diode D2 is reversed biased as the positive signal is inverted by the op-amp. So there will be no output. However, during the negative cycle of the input voltage, the diode D2 is forward biased and conducts. Therefore the above circuit works as a half wave rectifier.
Op Amp Applications as Peak Detector
The circuit above shows the use of op-amp as a peak detector. The circuit uses a diode and a capacitor. When Vout is more than Vin, the output is positive and the diode conducts. Whereas when Vout is less than Vin, the diode is reversed biased and does not conduct. The capacitor charges to the most positive value.
Op Amp Applications as Voltage Comparator
This is perhaps the easiest to comprehend. Two voltage sources are applied to the two terminals of the op-amp. Let the reference voltage be applied to the inverting terminal and the voltage to be measured is applied to the non-inverting terminal. If the voltage applied is greater than the reference voltage, we will get a positive output, else we will get a negative output.
