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Analog Electronics Workshop Slew Rate

Analog Electronics Workshop Slew Rate. March 13, 2013. Remember Capacitor Physics Constant Current -> Voltage Changes Linearly. Slew Limit. For slow moving or small signals i out < i out(max) For large rapid moving signals i out = i out(max) The output is slew rate limited

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Analog Electronics Workshop Slew Rate

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  1. Analog Electronics WorkshopSlew Rate March 13, 2013

  2. Remember Capacitor PhysicsConstant Current -> Voltage Changes Linearly

  3. Slew Limit • For slow moving or small signals iout < iout(max) • For large rapid moving signals iout = iout(max) • The output is slew rate limited • This is the fastest rate the output can change • The input is no longer a virtual short • Large input differential voltages are possible • Iout is constant so vout increases linearly across capacitor

  4. Slew Rate – Inside the Amplifier

  5. Slew Rate for Different Amplifiers

  6. Simulate Slew Rate OPA2188 Looking at the slope of the output signal. The rate of change is the slew rate.

  7. Simulate Slew Rate OPA2188 The input no longer has the virtual short. The output changes can not keep up with the input.

  8. Large Signal Step Response OPA827(Shows Slew Rate and Settling Time) SR = 10V / 0.4uS = 25V/uS (from graph) SR = 28V/uS (from data sheet table)

  9. Slew Rate Over Temperature

  10. Slew Boost Slows down as Vout approaches Vin.

  11. Current to Miller Capacitance IccWith and With out Slew Boost

  12. Slew Rate Lab • Simulation • Calculation • Measurement

  13. TINA Exercise-SR

  14. TINA Exercise-SR • Vin Settings • Square Wave Settings

  15. TINA Exercise-SR • Analysis->Transient • View->Separate Curves • Use cursors to measure slew rate

  16. NI myDAQ Exercise-SR • Populate U1 with OPA333 • Set J2 to pins 1-2

  17. NI myDAQ Exercise-SR • Launch FGEN • FGEN Settings • Square Wave • Frequency=10kHz • Amplitude=4Vpp • Signal Route=AO(1) • Run • Scope

  18. NI myDAQ Exercise-SR • Launch Scope • Scope Settings • Source = AI(0) • Scale V/Div = 500mV • Time/Div = 20us • Trigger Type = Edge • Run • Change Acquisition Mode to Run Once • Click Run for each acquisition • Turn Cursors On • Select CH 0 for both • Try to calculate slew rate

  19. NI myDAQ Exercise-SR Lab Results TINA Results Datasheet:

  20. Further Reading

  21. Backup/Extra

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