What is an operational amplifier, operational amplifier is explained in layman s terms

An introduction to operational amplifiers.

An amplifier (or "op amp" for short) is a circuit unit with a very high amplification. An operational amplifier is an electronic integrated circuit that contains a multi-stage amplification circuit. They are the input stage, the intermediate stage, the large stage and the bias circuit.

The red, green, and blue stages are the input, intermediate, and output stages, respectively. The input stage adopts a differential amplifier circuit with strong zero drift suppression ability, the intermediate stage often adopts a highly controversial co-emission stage amplifier circuit, the output stage generally adopts a power amplifier circuit with strong load capacity, and the function of the bias circuit is to provide a working voltage for the amplification circuit at all levels.

Two characteristics of the amplifier.

An ideal op amp must possess the following characteristics:

1.Infinite input impedance (zin= ) The ideal op amp input does not allow any current to flow in, that is, the current signal at the ends of the upper input signal v+ and v- is always zero, that is, the input impedance is infinite.

2.Output impedance approaching zero (zout=0): The output of an ideal op amp is a perfect voltage source, and the output voltage of the amplifier is always a certain value, i.e., the output impedance is zero, regardless of the current flowing to the amplifier load.

3.An important property of an ideal op amp is that the differential signal at the input has an infinite voltage gain in the open loop state, which makes the op amp very suitable for practical applications with negative feedback configuration.

4.An ideal op amp with an infinite common-mode rejection ratio (cmrr= ) can only respond to the difference between the voltages at v+ and v- (differential signals), i.e., only amplify the v+v portion. For the same part of the two input signals (common-mode signals) will be completely ignored.

What are differential signals and common-mode signals. Common-mode signal: When double-ended input, both signals are the same. Differential Mode Signal: When double-ended input, the phase difference between the two signals is 180 degrees.

The operating principle of the op amp is that for dual-supply powered op amps, the output can vary on both sides of the zero voltage, and the output can also be set to zero when the differential input voltage is zero. In a single-supply op amp, the output varies within a certain range between the power supply and ground.

The input potential of the op amp is usually required to be higher than a certain value for the negative supply and a certain value for the positive supply. The op amp is specially designed to allow the input potential to vary from negative to positive, even slightly above the positive supply or slightly below the negative supply. This op amp is called a rail-to-rail input op amp.

The output signal of the op amp is proportional to the signal voltage difference between the two inputs, in the audio segment there are: output voltage = A0 (E1-E2), where A0 is the low-frequency open-loop gain of the op amp (e.g. 100dB, i.e. 100000 times), E1 is the input signal voltage at the inverting terminal, and E2 is the input signal voltage at the inverting terminal.

1. Turn on MultiSim.

2. Click on the "Tools" option on the menu bar.

3. In the pop-up submenu, select "Circuit Wizard"."Op Amp Wizard"Options.

4. Set the parameters you need in the pop-up adjustment box, and then click Verify.

5. After the verification is completed, the point file spike is clicked to build the circuit.

6. After completing the construction, it can be placed on the diagram, (as shown in the bridge diagram), which completes the use of the operational amplifier.

1 Operational amplifier (opamp).

The integrated op amp has a co-directional input and a reverse input terminal, as shown in the figure below.

The output voltage satisfies the relationship, the final amplification of the integrated op amp is the differential mode signal, and in the case of no feedback, the amplification of the voltage is the differential mode open-loop amplification, which is recorded here, so when the op amp works in the best area, the voltage transmission characteristics of the integrated op amp are met as shown in the figure below;

When operating in the nonlinear region, that is, in the saturation state, the output voltage is or;

2 Hypothetical shortness and hypocrisy.

As mentioned earlier, the open-loop amplification of the integrated operational amplifier is very large, and the open-loop voltage amplification of the general purpose operational amplifier is more than 80 dB, but the output voltage of the op amp is limited, generally at 10V 14V, but the differential mode input voltage of the op amp is less than 1 mV, so the input can be approximately equipotential at both ends, which is equivalent to a short circuit. The larger the open-loop voltage amplification, the closer the potential of the two inputs is to equal, a characteristic called imaginary short.

The virtual break integrated operational amplifier has the characteristics of high input impedance, and the input resistance of the co-directional input terminal and the reverse input terminal is more than 1m, so the current flowing into the op amp at the input end is often less than 1ua, which is much smaller than the current of the circuit outside the input terminal. Therefore, the two inputs of the op amp can be regarded as an open circuit, and the greater the input resistance of the op amp, the closer the co-directional and reverse input ends are to the open circuit. When the op amp is in a linear state, the two inputs can be regarded as equivalent open circuits according to this characteristic, referred to as virtual breaks.