Experiment 1

Non-Inverting Amplifier

9.1 Objective:

To design and study the open loop gain from Non-Inverting Amplifier circuit.

9.2 Theory:

The op amp non-inverting amplifier circuit provides a high input impedance with all the other
advantages associated with operational amplifiers. The basic circuit for the non-inverting
operational amplifier is relatively straightforward. In this circuit, the signal is applied to the non-
inverting input of the op-amp.

In this way, the signal at the output is not inverted when compared to the input. However, the
feedback is taken from the output of the op-amp via a resistor to the inverting input of the
operational amplifier where another resistor is taken to ground. It has to be applied to the
inverting input, as it is negative feedback. It is the value of these two resistors that govern the
gain of the operational amplifier circuit as they determine the level of feedback.

Figure (1)

The gain of the non-inverting circuit for the operational amplifier:

In eq. above:

AV= voltage gain of op amp circuit.

R2 = feedback resistor resistance in Ω (Rf) R1 = resistance of resistor to ground in Ω (Rg)

9.3 Procedure:

1. Enter specific (input voltage) (2V) from the power supply device and draw input waveform
(Sin wave) by using Oscilloscope.

2. Connect the circuit shown in the figure (2).

Figure (2)

Connect the first terminal of OSC to the output terminal of opamp and second terminal of OSC
to the ground.

4. Turn on the circuit and Draw output waveform (sin wave) by using Oscilloscope. (Must be 4v
not opposite of in/p waveform)

9.4 Discussion:

1. Deduct the value of the gain G and compare it with theoretical value?

2. What is the non-inverting operational amplifier?

3. Calculate the average voltage (Av) of inverter Op-amp?

 Experiment 2

Inverting Operational Amplifier

Objectives

 to understand the main characteristics of operational amplifier circuits.

 to analyze and implement the inverting operational amplifier circuit.

 to illustrate the power supply regulation properties of operational amplifiers.

INTRODUCTION An Operational Amplifier is a very high-gain, direct-coupled amplifier that

uses feedback for control of its response characteristic. A direct-coupled amplifier is capable of
amplifying DC as well as time varying signals. The standard symbol for an op-amp is shown
below (Figure 2.1)

Figure 2.1 Standard symbol for operational amplifiers

The output voltage of an op-amp is the difference between the voltages applied to its input
terminals multiplied by its open loop gain, A. The output voltage is positive when the voltage
applied to the positive (non-inverting) input exceeds that applied to the negative (inverting)
input. An ideal op-amp would have an infinite open-loop gain, requiring that the difference
between V+ and V- be infinitesimally small in order for the output voltage to be finite. Thus, for
circuit analysis purposes, this voltage difference is assumed to be zero. Furthermore, the ideal
op-amp would have infinite input impedance and zero output impedance. These are, of course,
the ideal characteristics for a buffer amplifier that would make it possible to drive a low
impedance load with a large impedance source. For circuit analysis purposed, the current at the
input terminals is assumed to be zero, while the output voltage when driving a load is assumed to
be the same as the open circuit output voltage.

Operational amplifiers are versatile and useful devices. They can perform many functions, some
of which are: inverting, amplification, attenuation, summing, integrating, differentiating,
filtering, and signal generation (oscillators).

PROCEDURE 1. Prepare the power supplies for +VCC and -VCC to ensure the proper voltages,
+15V and -15V, respectively. See Figure 2.2.
Figure 2.2 Power supplies configuration

2. Connect +VCC and -VCC to a potentiometer as shown in Figure 2.3. This will provide a
variable-output DC signal source ranging from –VCC to +VCC , for input to the op-amp circuit.

3. Check this circuit with a volt meter to ensure that it provides the range of voltages desired.
The red voltmeter lead should be connected to the center terminal of the potentiometer and the
common ground between +VCC and -VCC. The way in which the power supplies are connected
to each other, and to the potentiometer produces four nodes, +VCC, -VCC, Vin and ground (or
reference).

Figure 2.3 Signal source configuration (Vin)

4. Turn the power supply off. 5. Connect the inverting amplifier circuit in Figure 2.4. Carefully
measure the values of the resistors that will be used in the circuit. Check the circuit carefully.
Figure 2.4 Inverting amplifier circuit

6. Turn on the power supply. Adjust the 10 kΩ potentiometer to achieve a Vin of 1 V. Measure
Vin and Vout and verify that the actual Vout is consistent with the theoretical

7. If the measured Vout is different from the theoretic, by more than 10%, troubleshoot the
circuit until is operating properly. Remember that the inverting amplifier has a negative gain.

8. Create a table with four columns labeled Vin, theoretical output voltage, Vout (the actual
output), and percent error. Leave enough room to record 10 rows of data.

9. Turn on the power supply, adjust Vin to -10 V, and carefully measure Vin and Vout. Increase
Vin from -10 V to +10 V in 1V increments, measuring Vin and Vout for each step. For each line
of data, compute and record the error between theoretical output voltage and Vout.

10. Adjust Vin to 2 V, and carefully measure Vin, +VCC, -VCC, V+(non-inv input) and V-(inv
input). Turn off the power supply.

11. By placing a 10µF capacitor in the feedback path (in Figure 2-6.) and a 1MΩ resistor at the
input we obtain a circuit that performs the mathematical operation of integration, see Figure 2.5.
Place a switch in the closed position (a jumper will work too) across the capacitor and adjust Vin
to 10 V.

12. Open the switch (t=0), and observe Vout(t) in the oscilloscope. Observe and measure the
time it takes for the output voltage to fall from 0V to -4V. Save an image of the oscilloscope
trace to include in your report.
Figure 2.5 DC integrator amplifier circuit

Questions

1. For the inverting amplifier, include in your report, plots of theoretical output voltage, Vout
(the actual output), and percent error vs. Vin, (i.e., three plots superimposed onto the same
graph).