ELG4135%20Electronics%20III%20Course%20Project%20Low%20Cost,%20Low%20Power%20Function%20Generator

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ELG4135 Electronics III Course Project Low Cost,
Low Power Function Generator

• By
• Md Amirul Bhuiya Norman Escobar
• December 1, 2006

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Introduction

• What are Function Generators?
• Function Generators can produce Square,
  Triangular and Sinusoidal waveforms over a wide
  range of frequencies and amplitudes as well as
  modulated waveforms (AM, FM, FSK) and signal
  noise.
• Why a Function Generator?
• Essential tool in Electrical Engineering
• Can be implemented with basic inexpensive
  components
• Most circuits needed have a direct relevance to
  the course
• Project Objectives
• To build a low-cost Function Generator capable
  of
• Producing Square, Triangular and Sine waveforms
  with amplitude control
• adjusting the waveform frequencies up to 1 MHz or
  higher
• Producing a Sine wave with minimal THD (ideally
  under 1).
• The function generator should be low cost

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Agenda

• In this Presentation we will talk about
• The Design
• Performance Results
• Advantages Disadvantages (Conclusion)

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Design

• Block Diagram
• Voltage Controlled Oscillator (VCO)
• Level Detector
• Sine Shaping Circuit
• Output stage (Variable Power Amplifier)

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Functional Block I Voltage Controlled Oscillator
Simplified Triangle Oscillator with single
voltage detector (Final VCO based on this
circuit)

• Wien Bridge Sine Oscillator
• Compensated Triangle Oscillator Using LM6365
• Triangle Oscillator with double Detector Circuit
• Crystal Oscillator

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Functional Block I Voltage Controlled Oscillator

• Final VCO design

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Functional Block IILevel Detector
Simplified Triangle Oscillator with single
voltage detector Final Selection

• Wien Bridge Sine Oscillator
• Compensated Triangle Oscillator Using LM6365
• Triangle Oscillator with double Detector Circuit
• Crystal Oscillator

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Functional Block III Sine Shaping

• Overdriven CA3080
• Breakpoint Sine Shaper
• BJT non-linear amplifier

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Functional Block IV Amplifier

• Variable Inverting Amplifier with Offset
  Adjustment

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Overall Circuit
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Performance Results

• Waveforms Produced
• Triangular, Square and Sinusoidal
• Overall Frequency Range 4 Hz 1.3 MHz
• Practical Frequency Range
• Triangle 4 Hz to 500 kHz
• Square 4 Hz to 1.3 MHz up
• Sine 30 kHz to 1.3 MHz up (independent)
• Sine 30 kHz to 500 kHz (dependent)

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Performance Results

• Duty Cycle Adjustment 1 - 80
• Amplitude Control 0 V 26 V p-p
• DC Offset Control 0V - /- 5 V
• THD of Sinewave
• 0.768 at 500 kHz, 50 D.C.
• 0.878 at 10 kHz, 50 D.C.
• 1.155 at 1.0 MHz, 50 D.C.

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Sine Shaper Frequency Response(Standalone)
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Sine Shaper Frequency Response(Integrated)
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Output Waveforms
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Output Waveforms(Frequency Modulated)
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Conclusion

• Practical Issues
• Cost of components alone is 106.30 not including
  power source
• Practical frequencies of the function generator
  are limited to above 30 kHz for the sine wave and
  below 500 kHz for the triangle wave due to the
  discharge control MOSFET which is too slow to
  turn off
• Output amplifier induces overshooting on square
  wave at higher frequencies

• Advantages
• Produces all the basic requirements of a function
  generator
• Good frequency range
• Good amplitude range
• Simple to design and build
• Expandable for modulation
• Minimal Circuit footprint

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References

• Adel S. Sedra and Kenneth C. Smith,
  Microelectronics Circuits. New York Oxford
  University Press, 2004.
• Bernie Hutchins, Electronotes. Contrasting
  sinewave generation in the analog and digital
  cases, http//www.synthtech.com/tutor/sine1.pdf.
• National Semiconductor, Appl. Note 271, pp. 9.
• John W. Fattaruso and Robert G. Meyer,
  Triangle-to-Sine Wave Conversion with MOS
  Technology, IEEE Journal of Solid-State
  Circuits, vol. Sc-20, No. 2, April 1985.
• Kim B. Östman, Sami T. Sipilä, Ivan S. Uzunov,
  and Nikolay T. Tchamov, Novel VCO Architecture
  Using Series Above-IC FBAR and Parallel LC
  Resonance, IEEE Journal of Solid-State Circuits,
  vol. 41, no. 10, October 2006.
• eCircuit Centre, Opamp Triangle-Wave Generator,
  2005, http//www.ecircuitcenter.com/Circuits/op_tr
  i_gen/op_tri_gen.htm
• National Semiconductor, Appl. Note 263, (Sine
  Wave GenerationTechniques).

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References

• Triangle to Sine Conversion (Nonlinear Function
  Fitting), class notes by M. H. Miller for ECE
  414, College of Engineering and Computer Science,
  University of Michigan-Dearborn, May 2004.
• National Semiconductor, LM6165/LM6265/LM6365 High
  Speed Operational Amplifier, pp. 9, May 1999.
• Analog Applications Journal, Design of op amp
  sine wave oscillators, Texas Instruments
  Incorporated, August 2000.
• National Semiconductor, Precise Tri-Wave
  Generation, Linear Brief 23, March 1986.
• MX.COM Inc, Appl. Note 20830065.001.

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Thank You