Kinds Of Operational Amplifiers
There are various types of electrical and electronic components which are typically used to design electronics projects and circuits. These components include, operational amplifiers, integrated circuits, microcontrollers, microprocessors, digital logic gates, analog to digital or digital to analog converters, and so on. Let us consider operational amplifier, which can be defined as an electronic device which takes differential input and thereby generates a single ended output and is termed as a DC coupled high-gain electronic voltage amplifier. In this article, let us discuss about the op amp circuits and basics.
Op Amp Circuit
The operational amplifier can be used to design various op amp circuits such as a differential amplifier, inverting amplifier, non-inverting amplifier, summing amplifier, voltage follower, instrumentation amplifier, oscillators, filters, comparators, integrators, differentiators, and so on. The op amp IC of LM741 is shown in the below figure which consists of eight pins and is a dual inline package.
The schematic symbol of op amp circuit which consists of various pins can be represented as shown in the below figure.
The op amp circuit model can be represented as shown in the below figure which consists of internal resistance Rin across the input terminals and output resistance Rout at the output terminal.
Op Amp Circuits
Now, let us discuss about a few frequently used op amp circuits such as inverting op amp, non inverting op amp, op amp integrator, and op amp comparator.
Inverting Op Amp
The inverting op amp circuit can be represented as shown in the below figure which consists of various pins such as input pins, output pin, and Vcc. Two resistors R1 and R are connected at the input terminal and between input-output terminals.
The gain of the inverting op amp circuit is given by the equation below
If both the resistors of inverting op amp circuit are equal, then the gain is equal to -1 and can be used as an inverting buffer in digital circuits. To design inverting op amp circuits, you need to keep in mind about various design considerations such as bandwidth, input impedance, and range of values for R1 & R2.
Non Inverting Op Amp Circuit
The non inverting op amp circuit can be represented as shown in the below figure which consists of various pins such as input pins, output pin, and Vcc. Two resistors R1 and R are connected at the input terminal and between input-output terminals.
The gain of the non inverting op amp circuit is given by the equation below
From the above equation, the gain must be always greater than one (>unity) and also positive. If the feedback resistor value is zero, then the gain of the amplifier reaches infinity which is practically limited to open loop differential gain of op amp circuits.
Op Amp Integrator
An electronic integrator based on the op amp circuit is termed as an op amp integrator, which generates an output proportional to the input integrated over time. By using pure resistances at the input terminal and feedback loop, the op amp circuits can be used as positive or negative feedback amplifiers or adder or subtractor type op amp circuits.
By replacing the pure resistance in the feedback loop with a capacitor, the op amp integrator circuit can be formed as shown in the above figure. The output voltage of the op amp integrator circuit is given by the following equation
The op amp comparator circuit is shown in the below circuit which consists of two input terminals which are fed with two voltage signals (desired to be compared).
The op amp circuits are generally extremely sensitive devices because of its large open loop gain, which makes it compatible for comparing the input with zero.
In practice, if the inputs V2 is greater than V1, then the output of the op amp comparator circuit will be driven to the positive supply voltage. If the inputs V2 is less than V1, then the output will be driven to the negative supply voltage.