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 3 4