Experiment Description

Experiment

Experiment E24    Inverting Amplifier

Objectives
  • Investigate the current that flows around the resistors in an inverting amplifier
  • Study the "virtual earth" at the inverting input of the operational amplifier
  • Explore the relationship between the input and output voltages in an inverting amplifier
  • Study how an inverting amplifier is used to amplify an a.c. signal
  • Illustrate a use of inverting amplifier
  • Study how an operational amplifier could perform mathematical operation
Description
In this activity, you will connect the operational amplifier to form an inverting amplifier.

In Experiment 1, you will study the relationship between the two currents of an op-amp in negative feedback, viz. Iin and If.

In Experiment 2, you will verify that the voltage across Rin is equal to the input voltage Vin. The input voltage and the current Iin are measured by voltmeter and milli-ammeter respectively.

In Experiment 3, you will compare the voltage gain to the ratio of Rin and Rf. The voltage gain is calculated from the measured input and output voltages, Vin and Vout.

In Experiment 4, you will apply an a.c. to the inverting amplifier. You will study how the signal is amplified by comparing the input and output signals using a dual trace CRO. The voltage gain is calculated again from the amplitudes of the signals.

In Experiment 5, you will connect a microphone at the input and a loudspeaker at the output to demonstrate the amplification of the inverting amplifier.

In Experiment 6, you will apply two different signals to the input of an inverting amplifier and study the relationship of the output voltage with the two input voltages.
Apparatus
operational amplifier unit [1]
dual 15 V d.c. power supply [1]
voltmeter (5 V, 10 V and 50 V) [2]
ammeter (1 mA, 10 mA and 100 mA) [2]
double beam CRO [1]
signal generator [1]
microphone [1]
loudspeaker [1]
Experiment