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Unformatted text preview: Scott Smith ENEE306-0104 24 October 2005 Lab Report Lab 3: Design and Build Your Own Compact Disk Hi Fi Audio System 3.1 Introduction Using the knowledge gained from the previous two labs, we will design an amplification system that will take a portable CD player as the input signal and produce a signal that can drive an 8 speaker. The amplifier should have constant gain within the audible frequency range (20 Hz to 20 kHz ). The amplitude of the output signal of the portable CD player is approximately 0.5 V . There will be two stages to the signal amplifier. First, the pre-amp stage increases the amplitude of the sound signal. Second, a current amplifier will allow the circuit to drive the load. 3.2 Design Considerations 3.2.1 Power to Load We will determine the maximum power that will be delivered to the load, an 8 speaker, using equation (1). ( ) ( ) = T L dt t I t V T P 1 (1) Assuming a perfect sine wave, L o L R V P 2 2 = (2) Here and , so = 8 L R V V o 10 = W P L 25 . 6 = (3) 3.2.2 Complimentary Symmetry Power Amplifiers The complimentary power amplifier has 1 v A , = i A , and low output resistance. A typical circuit is shown in figure 1. Q 1 is on when the input is greater than 0.7 V . Q 2 is on when the input is less than -0.7 V . The output resistance depends on which BJT is on at the time. = + > op n S mn on in R R g R V v 1 7 . (4) + = < p S mp op on in R g R R V v 1 7 . (5) v s R L R s Q 2 Q 1 V CC-V EE Figure 1 The power provided by the supply is, supply supply supply + + = I V I V P CC CC (6) L o R V I I 2 supply supply = = + (7) L o CC CC R V V I V P 2 2 supply supply = = + (8) The power conversion efficiency, , is the ratio of the power dissipated by the load to the power provided by the supply....
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- Spring '04