Integrator and Differentiator using IC 741 Op-Amp

Prerequisite: Know the theory about the experiment. Study the pin diagram and functioning of each pin of IC 741. Study how an integrator and a differentiator work.

Objective: To study the working of op-amp as differentiator and integrator.

Apparatus:

Bread board	1
Regulated power supply	1
CRO	1
IC 741	1
Resistors 10k, 100K	1 each
Resistors 1.5 k, 150	1 each
Capacitor 0.01F, 0.1F	1 each
Function generator 1 Hz to 2MHz	1
Connecting wires

Circuit diagrams:

Practical Integrator  R_f = 100k, R₁ = 10K, C_f = 0.1f

Fig 1. Integrator Circuit

Practical Differentiator R_f = 1.5 k, R₁ = 150, C_f = 0.1f, C₁ = 0.01f

Fig 2. Differentiator circuit

Procedure:

INTEGRATOR:

1. Connect the circuit as shown in fig 1.
2. Apply a symmetrical square wave of 2Vp-p amplitude and 1 KHz frequency.
3. Connect the input and output of the circuit to channel 1 and channel 2 of the CRO respectively and observe the waveforms.
4. Draw the waveforms along with the levels on a graph.
5. Compare the practical values with theoretical values.
6. Repeat the same for sine-wave.

DIFFERENTIATOR:

1. Connect the circuit as shown in fig 2.
2. Apply a symmetrical triangular wave of 2Vp-p amplitude and 1KHz frequency.
3. Connect the input and output of the circuit to channel 1and channel 2 of the CRO respectively and observe the waveforms.
4. Draw the waveforms along with the levels on a graph.
5. Compare the practical values with theoretical values.
6. Repeat the same for the sine-wave.

TABULAR  FORM:

INTEGRATOR:

DIFFERENTIATOR:              

Expected Waveforms:

a. Integrating square wave

b. Integrating sine wave waveform

c. Differentiator output for square wave

d. Differentiator output for sine wave waveform

Result: Designed and verified differentiator and integrator circuits using Op-Amp 741.

Outcome: After conducting this experiment students are able to design the circuits using op-amps to perform integration and differentiation operations for different waveforms.

Viva Questions:

1. Define integrator.

Ans: An integrator is a device to perform the mathematical operation known as integration, a fundamental operation in calculus. The integration function is often part of engineering and scientific calculations. Electronic analog integrators were the basis of analog computers.

2. Define differentiator.

Ans: A Differentiator is a circuit that is designed such that the output of the circuit is proportional to the time derivative of the input.

3. Write down output voltage formula for the integrator.

Ans: 

4. Write down output voltage formula for the differentiator.

Ans:

5. What is the output of the differentiator for square wave input?

Ans: Spikes

6. What are the problems in an ordinary op-amp differentiator?  What are the changes in the circuit of the practical differentiator to eliminate these problems?

Ans: Problems in an Ordinary op-amp differentiator are instability and high frequency noise. A Resistor is added in series with the capacitor at the input and a capacitor is added in parallel to the resistor in the feedback circuit in the practical differentiator to eliminate the above problems.

7. What are the problems in an ordinary op-amp Integrator?  What are the changes in the circuit of a practical integrator?

Ans: The gain of an integrator at low frequency is very high and the circuit goes to saturation. The feedback capacitor is shunted with a resistor in the practical integrator to overcome the above problem.

8. What is a lossy integrator?

Ans: The practical integrator is known as lossy integrator.

9. How a sine wave and cosine wave can be discriminated?

Ans: When t = 0, Sine wave amplitude is zero and the cosine wave amplitude is maximum.

10. Why integrators are preferred over differentiators in electronic circuits?

Ans: In differentiators, the gain increases at high frequency and are not stable.