Class B Amplifier Design
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The document discusses a high-efficiency, high-gain push/pull transistor power amplifier design with advantages such as minimal quiescent current and maximum efficiency of 78.5%. It outlines the key specifications, input/output characteristics, and compares costs for prototypes and mass production, providing detailed component pricing and PCB area requirements. Various references and links related to amplifier design and electronic principles are included for further reading.
Class B Amplifier Design
- 1. Ingram School of Engineering Texas State University San Marcos, TX December 5th, 2011
- 2. High efficiency High gain Push/pull transistors Power Amplifier › Av ≈ 1 › Ai > 1
- 3. Advantages: › Ideally, no quiescent current › High efficiency (max efficiency of 78.5%) Disadvantages: › Crossover distortion › Requires a biasing current › Q point stabilization D.J. Bates, A. Malvino. "Power Amplifiers," in Electronic Principles, 7th ed. New York: McGraw-Hill, 2007. pp. 392-397.
- 4. Input: Sinusoidal voltage, 50 Ω resistance Output: 2 – 16 Ω speaker Onboard 12 V supply High power gain High efficiency Minimum cost Single layer PCB Minimum PCB area
- 5. 14.0 12.0 10.0 Voltage (V) 8.0 6.0 4.0 2.0 0.0 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 Time (s)
- 6. Provides 5 V±5%, max 500 mA › Limits input signal to max 2.5 Vpk › Sufficient power Additional Cost › USB connector › Additional PCB area "7.3.2 Bus Timing/Electrical Characteristics". Universal Serial Bus Specification. USB.org
- 7. vin vout
- 8. ½ Vcc + 0.7V ½ Vcc ½ Vcc › VCB = 0.7 V › VBE = 0.7 V › Place each base 0.7 V above/below ½ Vcc - 0.7V emitter voltage
- 9. Avoid thermal runaway Stabilizing capacitor between bases › Keeps base voltages stable with AC swings
- 10. D.J. Bates, A. Malvino. "Power Amplifiers," in Electronic Principles, 7th ed. New York: McGraw-Hill, 2007. pp. 392-397.
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- 13. 0.8 0.7 Audible Range (20 Hz – 20 kHz) 0.6 0.5 0.4 0.3 fC1 = 16 Hz fC2 = 15 MHz 0.2 0.1 0 1E+0 1E+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7 1E+8 1E+9 Input Frequency (Hz)
- 14. 5 Vpk, 1 kHz Sinusoidal Input Signal 2.5 2 2 Ohm 4 Ohm 1.5 8 Ohm pout (W) 16 Ohm 1 0.5 0 0 0.00005 0.0001 0.00015 0.0002 0.00025 0.0003 0.00035 0.0004 0.00045 Time (s)
- 15. Single Prototype: $8.55 + PCB Components # per Circuit Unit Price ($) Cost ($) 1 kΩ resistor 5 0.33 1.65 500 µF capacitor 5 0.48 2.40 2N3904 transistor 3 0.43 1.29 2N3906 transistor 1 0.46 0.46 1N4002GP diode 4 0.50 2.00 100 µF capacitor 1 0.48 0.48 1N5242B Zener 1 0.27 0.27 Total: $8.55 Pricing from http://www.digikey.com as of Dec 3rd, 2011
- 16. Mass Production: $0.756 + PCB Components # per Circuit Unit Price ($) Cost ($) 1 kΩ resistor 5 0.036 0.18 500 µF capacitor 5 0.039 0.195 2N3904 transistor 3 0.033 0.099 2N3906 transistor 1 0.033 0.033 1N4002GP diode 4 0.048 0.192 100 µF capacitor 1 0.039 0.039 1N5242B Zener 1 0.018 0.018 Total: $0.756 Pricing from http://www.digikey.com as of Dec 3rd, 2011
- 17. 9 mm 50 mm PCB Area: 9 x 50 = 450 mm2 30 units per 10 x 16 cm board
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- 19. http://www.qrp.pops.net/AF-Basics.asp http://www.digikey.com http://www.ece.drexel.edu/courses/ECE-E352/ClassABAmp.pdf http://vijayatronics.info/Notes/ch-2%20ampli.pdf http://www.electronics-tutorials.ws/amplifier/amp_6.html http://www.usb.org
- 20. Dr. Semih Aslan Ingram School of Engineering Texas State University
- 21. Diagram Supply Biasing Stability Efficiency Gain Frequency Load Cost PCB