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University of Puerto Rico at Humacao

Department of Physics and Electronics

Laboratory 5: Op- Amp Applications

Jorge L. Castro TorresStudent Number: 842-10-1344

Eduardo Vega Lozada

Student Number: 842-10-9186

FISI 4088- 001

March 13, 2014


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Laboratory 5: Op- Amp Applications

1 Objective or PurposeThe objective of this experiment is to construct a zero/scale amplifier and a current to

voltage converter using the LM741 operational amplifier.

2 Summary of Related TheoryZero/Scale Amplifier:

The zero scale amplifier is an inverting amplifier with variable resistors at the entrance and the

offset to adjust the gain and offset respectively. If we think of an op-amp connected as an

inverting amplifier with a controlled amount of voltage gain is shown in Figure #. The input

signal is applied through a series input resistor R i to the inverting (-) input. Also, the output is

fed back through Rf to the same input. The non-inverting (+) input is grounded.

Figure 1: Inverting Amplifier.

In particular, the concept of infinite input impedance is great value. An infinite input

impedance, then there must be no voltage drop between the inverting and non-inverting

inputs. This means that the voltage at the inverting input terminal is referred to as virtual

ground. This condition is illustrated n Figure 1a. Since there is no current at the inverting input,

the current through Ri and the current through Rf are equal, as shown in Figure 1b.


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Figure1: Virtual (a) and Iin =If and current t the inverting input (I1) is 0.

The voltage across Ri =Vin because the resistor is connected to the virtual ground at the inverting

input of the op-amp. Therefore,

Also, the voltage across Rf equalsVout because of the virtual ground, and therefore,

Since If=Iin,

Rearranging the terms,


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3 Materials and EquipmentA. Table 1: Materials and Equipment

Name Manufacturer Model Serial

Multimeter Hewlett Packard 34401A US36077916

Power Supply Hewlett Packard E3631A MY51170062

Oscilloscope Hewlett Packard 54600B US39150280

Breadboard Global Specialties PB- 505

Wave Generator Hewlett Packard 33120A US36033305

Table 2: Materials

Component Quantity Value

LM471 1 ---------

Resistor 1 2k

Resistor 1 150k

Potentiometer 1 5k


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4 Procedure and Diagrams

5 Calculations and Graphs6 Error Analysis

Once the experiment was finished, the calculations required for getting theresults were done. The theoretical and experimental results were practically

even meaning that there were almost no errors in the values obtained. Since theranges of voltage and current for this circuit were symmetrical, an offset

adjustment was not required. We used a potentiometer to adjust the loadresistance, bringing possible sources of error when calculating for a fixed value

of the RL.

7 ConclusionIn this experiment we worked with the LM471 Operational amplifier as a

voltage to current converter with floating load (not connected directly to

ground). We calculated the output voltage taking into account that the voltage

ranged from -1.5V to 1.5V and current from -5mA to 5mA. The symmetry ofthese ranges helped us to avoid other adjustments such as offset voltage. Addinfo about the output current obtain compared to the one calculated through

RL.


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8 Summary

9

Data sheets

10References1- Op-Amps. Retrieved from

http://www.facstaff.bucknell.edu/mastascu/elessonshtml/OpAmps/OpAmp2.htmlon

March 12, 2014.

2- 2N3904. Retrieved fromhttp://www.fairchildsemi.com/ds/2N/2N3904.pdf March 12, 2014.

3- 2N3906. Retrieved fromhttp://www.ece.rice.edu/~jdw/data_sheets/2N3906.pdfon March12, 2014.

4- Floating Load Amp. Retrieved fromhttp://nptel.ac.in/courses/Webcourse-contents/IIT-ROORKEE/Analog%20circuits/lecturers/lecture_13/lecture13_page2.htm

on March12, 2014.
http://www.facstaff.bucknell.edu/mastascu/elessonshtml/OpAmps/OpAmp2.html%20on%20Marchhttp://www.facstaff.bucknell.edu/mastascu/elessonshtml/OpAmps/OpAmp2.html%20on%20Marchhttp://www.facstaff.bucknell.edu/mastascu/elessonshtml/OpAmps/OpAmp2.html%20on%20Marchhttp://www.facstaff.bucknell.edu/mastascu/elessonshtml/OpAmps/OpAmp2.html%20on%20Marchhttp://www.fairchildsemi.com/ds/2N/2N3904.pdfhttp://www.fairchildsemi.com/ds/2N/2N3904.pdfhttp://www.ece.rice.edu/~jdw/data_sheets/2N3906.pdfhttp://www.ece.rice.edu/~jdw/data_sheets/2N3906.pdfhttp://www.ece.rice.edu/~jdw/data_sheets/2N3906.pdfhttp://nptel.ac.in/courses/Webcourse-contents/IIT-ROORKEE/Analog%20circuits/lecturers/lecture_13/lecture13_page2.htmhttp://nptel.ac.in/courses/Webcourse-contents/IIT-ROORKEE/Analog%20circuits/lecturers/lecture_13/lecture13_page2.htmhttp://nptel.ac.in/courses/Webcourse-contents/IIT-ROORKEE/Analog%20circuits/lecturers/lecture_13/lecture13_page2.htmhttp://nptel.ac.in/courses/Webcourse-contents/IIT-ROORKEE/Analog%20circuits/lecturers/lecture_13/lecture13_page2.htmhttp://nptel.ac.in/courses/Webcourse-contents/IIT-ROORKEE/Analog%20circuits/lecturers/lecture_13/lecture13_page2.htmhttp://nptel.ac.in/courses/Webcourse-contents/IIT-ROORKEE/Analog%20circuits/lecturers/lecture_13/lecture13_page2.htmhttp://www.ece.rice.edu/~jdw/data_sheets/2N3906.pdfhttp://www.fairchildsemi.com/ds/2N/2N3904.pdfhttp://www.facstaff.bucknell.edu/mastascu/elessonshtml/OpAmps/OpAmp2.html%20on%20Marchhttp://www.facstaff.bucknell.edu/mastascu/elessonshtml/OpAmps/OpAmp2.html%20on%20Marchhttp://www.facstaff.bucknell.edu/mastascu/elessonshtml/OpAmps/OpAmp2.html%20on%20March

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