Slide show developed as part of school project. My contribution to group, in addition to engineering and circuit design, was creating and organizing a Power Point presentation to summarize our 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.

11. 

12. 

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

18. 

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