ece137a_lab2_2008 - lecture, but are also in the notes and...

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1 ECE137A, Lab Project #2 In this project, you will design, build, and test a small audio power amplifier to drive a loudspeaker. This will be used in conjunction with later lab projects. The speaker is an 8 Ohm load. A differential input is required. The circuit specifications are as follows All testing is with an 8 Ohm load resistance. Voltage Gain: 10, plus or minus 20%, measured at 1 kHz. Input impedance: 1000 Ohms or more. Variation in gain less than +/- 1 dB between 100 Hz and 10 kHz ---this sets a minimum size on bypass and coupling capacitors. Peak-peak output swing before clipping: greater than 5 volts peak-peak. Power supplies: Positive and negative 5 volts. The input is to be differential, with > 50 dB CMRR at 1 KHz. The amplifier can only be partially AC coupled: DC blocking capacitors are allowed on the input, if desired, and an output DC blocking capacitor is also allowed but is not recommended. It is better to design for zero volts on the output. Use of a push-pull class AB output stage is strongly suggested: these will be discussed in
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Unformatted text preview: lecture, but are also in the notes and in the book, so you can read ahead. Beware of thermal runaway: the thermal stability factor, K, given below, must be less than 1 or the push pull circuit can spontaneously destroy itselt. Vcc is the supply voltage. Re the emitter degeneration, and the theta terms are thermal resistances. e e case junction cc R r V C mV k + + + = ) ( ) / 2 . 2 ( ambient heatsink heatsink case case junction is given on the transistor datasheet, heatsink case should be less than 2 C/W if you firmly attach the transistor to the heatsink with minimal air gaps, thermal conductive compound, and a thin mica insulator. ambient heatsink is discussed on the web ( ) , who give ) / ( / 50 2 cm W C A ambient heatsink , where A is the surface area of the heat sink. Heat sink surfaces should be vertical for best thermal convection....
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This note was uploaded on 08/06/2008 for the course ECE 137AB taught by Professor Rodwell during the Winter '08 term at UCSB.

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