- 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.
Applications of an op amp include inverting and non-inverting amplifiers, adders, differentiators, integrators, converters, log amps, precision rectifiers, peak detectors and comparators. A linear amplifier like an op amp has a high open loop gain, high input impedance and low output impedance. It has high common mode rejection ratio. Those traits, used with feedback, are what the applications of op amp below rely on.
Op Amp applications as Inverting Amplifiers
Op-Amp can be used as an inverting amplifier, the first closed-loop application below.
- The inverting circuits, implemented with an Op-Amp, are more stable, distortion is lower and they give a cleaner step response than many open-loop stages.
- When Op-Amp is applied in a closed loop, there is a linear relationship between input and output until the output hits the rails.
- 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 phase inversion. In a discrete transistor chain, at least two transistor stages are needed to do this.
- High input impedance compared to Inverting input.
- Adaptable voltage gain.
- The signal source is isolated from the load by the op-amp output stage.
Op Amp application as a Phase Shifter
An Op-Amp phase-shifter or level-shifter adds a DC offset so a signal that sits on a raised bias can be returned toward ground. Discrete transistor stages can stack DC levels; the op-amp circuit in the diagram does that offset with feedback rather than at an emitter node.
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.
A positive scaler uses the non-inverting form so the output equals the input multiplied by a positive constant, still with negative feedback around the loop.
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 through resistors to the inverting terminal of the op-amp. The non-inverting terminal is grounded. Feedback holds the inverting pin at virtual ground. The output voltage is proportional to the sum of the input voltages, with a sign set by the resistor ratios.
Op Amp Applications as a Differential Amplifier
Differential Amplifier is a useful blend of both the inverting amplifier and non-inverting amplifier, used to amplify the difference between 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 reject noise that is common to both wires of a protected cable or twisted pair, which is mostly used to cut 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, over a limited band set by the RC time constant. The derivation is omitted; the use is 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, so the circuit performs the mathematical operation of integration as the output varies with the input and duration of the signal, until the capacitor voltage hits the rails.
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 input 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 over a limited range, and it is temperature sensitive, so it can be used as a logarithmic amplifier in that band.
Op Amp Applications as Half Wave Rectifier
The circuit diagram above shows the usage of an op-amp as a half wave rectifier. During one half-cycle of voltage, diode D2 is reverse biased as the signal is inverted by the op-amp, so that path does not feed the load. During the other half-cycle, diode D2 is forward biased and conducts. Therefore the above circuit works as a precision half wave rectifier, with the conducting polarity set by the drawing.
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 Vin is more than the stored capacitor voltage, Vout drives the diode on and the capacitor charges toward that peak. When Vin then falls, Vout can reverse and the diode is reverse biased and does not conduct. The capacitor holds the most positive value until it leaks or is reset.
Op Amp Applications as Voltage Comparator
Two voltage sources are applied to the two terminals of the op-amp. With the reference voltage on the inverting terminal and the voltage to be measured on 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, each limited by the supply rails and slew rate.
