Various Op Amp Applications in Electronics

An operational amplifier is an integrated circuit that operates as a voltage amplifier. An op amp as a differential input. That it has two inputs of opposite polarity. An op- amp as a single input of opposite polarity. An op-amp has a single output and a very high gain, which gives that the output signal.

Generally, we use many applications by using op-amps like

  • Differential amplifiers
  • Inverting amplifiers
  • Non-inverting amplifiers
  • Voltage followers
  • Summing amplifiers
  • Instrumentation amplifiers

It will act as a some oscillators

  • Wien Bridge oscillators

It will act as some filters by using operational amplifiers

  • Operational amplifiers can be used in construction of active filters, providing high pass, band pass reject and delay functions. The high input impedance, gain of an op-amp allow straightforward calculation of element values.

Some of the operational amplifiers can be generally used as a comparators like

The basic comparator schematic diagram as shown in fig

Comparator
Comparator

Now we will discuss various types of differential amplifiers in details step by step

Differential  Amplifiers

Differential amplifier amplifies the difference between two voltages, making this type of operational amplifier circuit a sub tractor unlike a summing amplifier which adds or sums together the input voltages. These types of operational amplifier circuits are commonly known as a differential amplifier. By connecting each input intern to 0v ground we can use superposition to solve for the output voltage Vout. The equation of the Vout is

Differancial Amplifier
Differancial Amplifier

V out=-v1(R3/R1)+V2(R4/R2+R4)(R1+R3/R1)

In this equation R1=R2;and R3=R4 then by using this equation

V out=R3/R1(V2-V1) .

If all these resistors all of the if same ohmic values, That is R1=R2=R3. Then the circuit will become Unity gain differential op amps.

Applications of Differential Amplifiers

  • It is used as a series negative feedback circuit by using op amplifier
  • Generally, we use differential amplifier that acts as a volume control circuit.
  • The differential operational amplifier can be used as an automatic gain control circuit.
  • Some of the differential operational amplifier can be used for Amplitude modulation.

Inverting Operational Amplifiers

An inverting amplifier is a closed loop circuit the operational amplifier circuit is connected with the feedback to produce the feedback operation. When dealing with op amplifiers there are two very important rules to remember about inverting amplifier, these are no current flows to the input terminal. And that V1 is always being equal to the V2. However, in real world op amp circuits both of these rules are slightly broken.

This is because the junction of the junction of the input and feedback signal is at the same potential as the positive input, which is at 0 volts or ground then the junction is a virtual earth.

Because of the virtual earth node the input resistance of the amplifier is equal to the value of the input resistor, R in and the closed loop gain of the inverting amplifier can be set by the ratio of the two external resistors.

We said above that there are very important rules to remember about inverting amplifier or any operational amplifier is shown bellow

  • No current flows to the input terminals
  • The differential input voltage is 0 as V1=V2=0.

Then by using two rules we can derive the equation by calculating the closed loop gain of an inverting amplifier

Inverting Amplifier
Inverting Amplifier

I=(Vin-Vout)/(Rin+Rf)

Therefore I=(Vin-V2)/Rin

I=(V2-Vout)/Rf

The closed loop Gain is given as Vout/Vin=-Rf/Rin

The closed loop voltage gain is equal to Vout = –Rf/Rin*Vin

The negative sign in the equation indicates an inversion of the output signal with respective to the input as its 180 degrees out of the phase

Applications of the Inverting Amplifier

  • Inverting amplifier is use full for voltage adder or summing amplifier
  • Inverting amplifier is applicable for the scaling summer amplifier.
  • It is applicable for balanced amplifier.

Non-Inverting Amplifier

Non inverting amplifier where the output is in the same sense or in phase with the input. In this circuit the signal is applied to the non inverting input of the operational amplifier . However the feedback is taken from the output via a resistor to the inverting input of the operational amplifier where another resistor is taken to ground. The basic non inverting amplifier is shown in fig

Non-inverting Amplifier
Non-inverting Amplifier

The gain of the non inverting amplifier circuit of the operational amplifier is easy to determine and the output of the non inverting amplifier is same as the input voltages . So, that the gain of the amplifier is exceedingly high.

As the input to the op amp draws no current this means that the current flowing in the resistors R1 and R2 and the voltage at the both inputs is same. The equation of the non inverting amplifier can be called as a Vout/Vin =Av=1+R2/R1.

Applications of Non-inverting Amplifier

  • A non inverting amplifier uses a voltage divider bias negative feedback connection.
  • Here the voltage gain is always greater than 1.

Voltage Follower

A voltage follower is also called as a unity gain amplifier, a buffer amplifier and an isolation amplifier) is an op-amp circuit which has a voltage gain of 1.

This means that the op amp does not provide any amplifications to the signal. The reason it is called as a voltage follower is because the output voltage does not provide the input voltage.

Voltage Follower
Voltage Follower

An op-amp circuit is very high input impedance. This high input impedance is a reason voltage follower is used. The load demands and draws a huge amount of current. This causes a huge amount of power to be drawn by the power sources. Voltage followers are also called as a voltage buffer.

Applications of Voltage Follower

  • High input impedance and a very low output impedance
  • Voltage followers are generally used to isolate stages from each other.
  • Voltage follower is also called as a voltage buffer.

Summing Amplifier

Summing amplifier is one of the application of inverting operational amplifier, but if we add another input resistor equal in values to the other input resistor, Rin we end up another op amp is called as summing amplifier.

Summing Amplifier
Summing Amplifier

It is also as a voltage adder circuit symbol in above summing amplifier input voltages V1,V2,V3 and input resistors are Rin, Feedback resistors are Rf. So summing applier is shown in fig

-Vout=Rf/Rin(V1+V2+V3…etc)

Applications of Summing Amplifier

  • Summing amplifier is also called as a bipolar amplifier or a uni-polar converter.
  • Summing amplifier converts digital to analog converter

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