# Instrumentation Amplifier - Department of Biomedical Engineering

```Instrumentation Amplifier
Wei Lin
Department of Biomedical Engineering
Stony Brook University
Instructor’s Portion
Summary
This experiment requires the students to build an instrumentation amplifier
using operational amplifier. The students will estimate the gain of the
amplifier and use ELVIS work station to measure the real gain of the
amplifier.
Uses
This lecture applies to all courses of virtual instrumentation.
Equipment List

Computers

LabVIEW 8.6

NI-ELVIS benchtop workstation

LabVIEW Student Edition
References
Student’s Portion
Introduction
The students will build the instrumentation amplifier based on the provided
schematics diagram. They will use the rules of ideal operational amplifier to
estimate the gain of the built instrumentation amplifier. They are also required
to develop a protocol to measure the gain using the signal generator in ELVIS
workstation and the data acquisition VI developed in the previous project
titled “Data Acquisition Using NI-DAQmx VIs”.
Objectives

Build an instrumentation amplifier
1



Measure the gain of the amplifier
Measure the combined frequency response of the instrumentation
amplifier and the filters built in the previous project
Data acquisition using LabVIEW
Theory
The instrumentation amplifier is the popular preamplifier for signal
conditioning. It offers high impedance and common mood rejection ratio
(CMRR). It composes of three amplifiers. The gain of the amplifier is
determined by the resistor network based on the rules of ideal operational
amplifier. Detailed descript can be found in the textbook “Medical
Instrumentation, Application and Design”. The schematics design is in
appendix.
Lab Procedure
1.
2.
3.
4.
5.
Keep ELVIS workstation power off.
Identify the pin assignment of the operational amplifier (LF353).
Get familiar with the layout of breadboard.
Place two LF353 on the breadboard.
Place the resistors on the breadboard and connect the pins of the
operational amplifiers using these resistors if possible.
6. Create lines of power supplies (+15V, -15V) and ground.
7. Connect the +15V to pin 8 of both LF353s (Vcc) and -15V to pin 4 of
both LF353 (Vee).
8. Connect the ground of the circuit.
9. Verify that all the connections are correct.
10. Connect one input terminal to ground and the other to FUNC OUT
terminal. For signals less than 5Hz, use your LabVIEW code to
generate the signal. All signals are sine waves.
11. Turn on the ELVIS workstation.
12. Launch LabVIEW and ELVIS.
13. Measure the gain of the amplifier by comparing the amplitude of the
input and output signal.
Lab Report
The lab report includes three projects: analog output using LabVIEW,
filters and instrumentation amplifier. It should have the following:
1. The experiment objectives
2. The experiment procedure, theory and your protocol to measure the
gain of the amplifier.
3. Results
4. Discussion
5. Due on
2
Appendix: Schematics of the instrumentation Amplifier
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4
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