Experiment 8: Design an Inverting and Non-Inverting Amplifier Using Op-Amp (IC 741)

Design an inverting and Non-Inverting Amplifier using

OPAMP(IC741)

Objective:-

1.      Design the circuit diagram. Determine the theoretical output voltage of inverting and non-inverting amplifier. Take the reading and draw the input & output  waveform

Equipments required:-  1)  Multimeter, CRO, Bread Board, Function generator for input source,  Power Supply ±15

Components Required:-1) Op Amp (IC741) – 1 No.     2) Resistors R_in=1k,  R_f= 3.9K

Theory:-An OPerational AMPlifier or OPAMP is a very high gain differential amplifier with high input impedance and low output impedance. The basic circuit is made using a difference amplifier having two inputs and one output. The plus (+) input produces an output that is in phase with the signal applied, whereas an input to the minus (-) input results in an opposite polarity output.

Most existing OPAMPs are produced on a single semi-conductor substrate as an Integrated Circuit (IC741). The Pin diagram is

.

The two most widely used constant gain amplifier are the inverting and non-inverting amplifier.

Circuit Diagram 

Inverting amplifier

Inverts and amplifies a voltage (multiplies by a negative constant)

\[{V_{out}} =  - \frac{{{R_f}}}{{{R_{in}}}}{V_{in}}\]

• Z_in = R_in (because V ₋ is a virtual ground)

Non-inverting amplifier

 

Amplifies a voltage (multiplies by a constant greater than 1)

\[{V_{{\rm{out}}}} = {V_{{\rm{in}}}}\left( {1 + \frac{{{R_2}}}{{{R_1}}}} \right)\]

input impedance   \[{Z_{{\rm{in}}}} \approx \infty {\mkern 1mu} \]

1. The input impedance is at least the impedance between non-inverting ( + ) and inverting ( − ) inputs, which is typically 1 MΩ to 10 TΩ, plus the impedance of the path from the inverting ( − ) input to ground (i.e., R₁ in parallel with R₂). 
2. Because negative feedback ensures that the non-inverting and inverting inputs match, the input impedance is actually much higher.

Result Table:-

Type of Amplifier	Input AC voltage	Output Voltage	Calculate the theoretical Gain	Measure Practical gain	Measure phase difference
Inverting
Non-Inverting

PROCEDURE:-

1. The OPAMP was set up as per the circuit diagram (inverting or non-inverting as the case may be). 
2. Power supply was provided and the gain of the amplifier was measured by noting down the output voltage with a multimeter. 
3. The gain was determined with  the value of feedback resistor(R_f)  keeping the input resistance constant (R_in).