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quiz_1_2007_solution

# quiz_1_2007_solution - Question 1A You would like to design...

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Question 1A You would like to design an amplifier to use your MP3 player in your car. The amplifier should not provide less than 40W of signal power to a speaker whose resistance is 10 . The MP3 player’s audio jack provides a 100mV signal and has a resistance of 5K . Out of your drawer, you take out three amplifier stages: a) High input resistance: R IN = 1M , R OUT = 10K , A VO = 10V/V b) High gain: R IN = 10K , R OUT = 1K , A VO = 100V/V c) Low output resistance: R IN = 10K , R OUT = 10 , A VO = 1V/V 1) What kind of amplifier is this (A V , A IS , R MO , G MO )? Based on the configuration to best maximize the gain for a single stage amplifier of this type, in what order should the amplifiers be connected? A V , or Voltage amplifier. The amplifiers should be put (from input to output): (a), (b), (c) because you want high Rin and low Rout. 2) What is the minimum output voltage required to drive the speaker? What is the minimum gain? P = V 2 / R L Æ V = 20 V Therefore A VO = 20V/0.1V = 200 V/V 3) Based on the configuration in (1), what gain can you realize? What is the resulting output and output power? Gain = (1) * (100) * (10) * (10/20) * (10K/11K) * (10K/20K) * (1M/(1M + 5K)) Gain = 226.1 V/V Therefore load voltage = 226.1 V/V * 0.1 V = 22.61 V Power = V 2 / R L = 51.1 W

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Question 3A The circuit below contains two diodes having n=1. Solve parts a) and b) using the constant voltage drop model (CVDM) a) (2 pts) If the resistance R = 50 and V1 = V2 = 5 V, determine the current flowing in each diode. Voltage across R is 5 – 0.7 = 4.3 so current in R is 4.3/50 = 86mA and half of that (43 mA) flows in each diode. b) (2 pts) If the resistance R = 50 and V1 = 5 V and V2 = 6 V, determine the current flowing in each diode. In this case, D1 is clearly off (I=0) and voltage across R is 5.3 so there is 5.3/50 =106mA of current in D2. c) (3 pts) Assume the resistance R = 50 and V1 = V2 = 5 V as in part a). This time, use the exponential model I = Is·exp(V/nV T ) for each diode and assuming that saturation current Is = 1x10 -12 . Solve for the voltage drop across each diode.

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