INSTRUMENTATION & CONTROL

Objective

To find slew rate of op-amp (IC741C).

Components

Operational amplifier IC (µA741)
Resistor (10kΩ, 1/4W, carbon)
Bread board
CRO probe (4 nos)
Hook up wires
CRO
Function generator

Theory

The important frequency related parameter of an operational amplifier is the slew rate. The slew rate is the is the maximum rate of change of output is the maximum rate of change of output voltage with respect to time , usually specified in V/µs. the equation of slew rate is
SR = ΔV0/Δt V/µs
Ideally, slew rate should be infinitely so that operational amplifier output voltage would change simultaneously with the input practical operational amplifiers are available with slew rates from 0.1V/µs to well above 1000V/µs. Generally, the slew rate is specified for unity gain and is measured by applying a stop input (DC) voltage. The slew rate has important effects on both amplifier circuits. Since the open loop voltage gain is very large , the output will go to above +14 volt and then -14 volts each time the input since wave crosses time taken by the output to go form +14 volts to -14volts can be determine by using the slew rate of the 741C listed in the datasheet. The741C has a typical slew rate of 0.5V/µs. Slew rate limiting accurse with all large fast-changing signals. If slew rate is exceeded , distortion of the of the output wave forms results

Procedure

1. Before connecting the circuit measure the output offset voltage and then connect the circuit as shown in figure.
2. For finding slew rate apply square wave input to the operational amplifier from function generator and get the output to the CRO.
3. Now get the slew rate from the ratio of maximum rate of change of output voltage to the change of time

Precautions

- Switch on the battery only after all the connection of the circuits are connected.
- Never remove the wires when the battery is on as it can damage the IC (741C).