Opamp 741

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EXPERIMENT
37

Noninverting voltage feedback
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There are four Basic types of negative feedback, depending on which input is used andwhich output quantity is sampled. Noninverting voltage feedback results in an almost perfect voltage amplifier, one with high input impedance, low output impedance, and stable voltage gain. Thenegative feedback also reduces nonlinear distortion and output offset voltage.

In this experiment you will work with noninverting voltage feedback. First, you will see how accurate the formula forclosed-loop voltage gain is. Second, you will see how stable the voltage gain is for different op amps. Third, you will calculate and measure output offset voltages for different feedback resistors. Alsoincluded are troubleshooting, design and computer options.
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REQUIRED READING

Chapter 16(secs. 16-1, 16-2) of electronics principles

EQUIPMENT.
1 audio generator
2power supplies +/- 15 volts
9 ½ w resistors: 2 1k, 2 10k, 22k, 33k, 47k, 68k, 100k
3 op amps: 7411c

STABLE VOLTAGE GAIN.

5.- assume R1 is 33Koms in fig. 37-1. calculate and record theclosed-loop voltage gain (table37-2).
6.-conect the circuit with R1 equals 33Kohms. Measure Vout and calculate Acl. Record this measured value in table 37-2. Calculate the closed-loop voltage gain withAcl=Vout/Vin. Record this as the measured Acl
1 VOM (analog or digital multimeter)
1 oscilloscope
2 capacitors .47micro farads

PROCEDURE

VOLTAGE AMPLIFIER
1.- in fig. 37-1, assume R1 equals10kohm. Calculate the closed loop voltage gain. Record Acl in table 37-1.
2.- repeat step 1 for the other values of R1 shown in table 37-1.
3.-conect the voltage amplifier of fig. 37-1 with R1 equals to10kohms. Set the audio generator to 1KHz at 100mV p-p. measure Vout. Calculate closed-loop voltage gain with Acl=Vout/Vin
4.- repreat step 3 for the other values of R1 listed in table 37-1.

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