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Analog Electronics Workshop Input/Output Limitations

This workshop addresses common-mode voltage (Vcm) and output swing limitations in analog electronics. It covers key concepts such as Vcm range, output swing ranges, and the implications for circuit design. Through hands-on exercises with NI myDAQ and simulations using TINA, participants will learn to identify Vcm violations and manage output swing constraints. The content includes definitions, measurement techniques, and practical examples to enhance understanding of these critical limitations in analog circuits.

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Analog Electronics Workshop Input/Output Limitations

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  1. Analog Electronics WorkshopInput/Output Limitations Rev 0.2 March 13, 2013

  2. What’s Wrong?

  3. Common Mode Voltage Definition

  4. Input and Output Swing Vcm Range Output Swing Vcm Vout

  5. Vcm – Two Examples Vcm = 0V Vcm = 5V

  6. Input Stage Output Stage VSAT VBE

  7. Translating the Data Sheet -2.6V< Vcm < 1.0V -2.95< Vout < 2.95V -2.6V< Vcm < 1.0V

  8. Vcm or Output Swing Problem? Vcm=Vin! • Remember • -2.95V<Vout<2.95V • -2.6V<Vcm<1.0V • What is the common-mode voltage? • This is a Vcm violation!

  9. Vcm Lab • Measurement

  10. NI myDAQ Exercise-Vcm Populate U1 with OPA735 Set J2 to 1-2 position

  11. NI myDAQ Exercise-Vcm • Launch Scope • Scope Settings • Scale V/Div = 500mV • Time/Div = 200us • Trigger Type = Edge • Run

  12. NI myDAQ Exercise-Vcm • Launch FGEN • FGEN Settings • Triangle Wave • Frequency=1kHz • Amplitude=4Vpp • Signal Route=AO(1) • Run

  13. Further Reading

  14. NI myDAQ Exercise-Vcm TINA Results Lab Results

  15. Output Swing Lab • Simulation • Measurement

  16. TINA Exercise

  17. TINA Exercise • Vin Settings • Triangular Wave Settings

  18. TINA Exercise • Analysis->Transient • View->Separate Curves

  19. Vcm or Output Swing Problem? Vcm=0V! Output Swing Violation! • For OPA277 • -2.0V<Vout<1.3V (RL=10k) • -0.5V<Vcm<0.5V • What is the common-mode voltage? • We can’t violate Vcm in this configuration!

  20. NI myDAQ Exercise-Output Swing • Populate U2 with OPA277 • Inverting Configuration

  21. NI myDAQ ExercisesOutput Swing • Stop Scope • Settings • Source=AI(1) • Scale V/Div = 500mV • Time/Div = 200us • Trigger Type = Edge • Run

  22. NI myDAQ ExerciseOutput Swing • Stop FGEN • Settings • Triangle Wave • Frequency=1kHz • Amplitude=160mVpp • Signal Route=AO(0) • Run

  23. NI myDAQ ExerciseOutput Swing TINA Results Lab Results

  24. I/O Limits Homework

  25. 1. For the circuit below: The output reads -260mV. The offset is 30uV typical. Why is the output so large?

  26. 1. For the circuit below: The output reads 171mV. The offset is 30uV typical. Why is the output so large?

  27. Revisions • 0.2 • Added homework • Added Lis / Kay presentation on limits.

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