EE 164 Problem Set 10 Spring 2005 Problem 1: Design an analog modulator like that shown in the below figure by using a silicon transistor. For this transistor, 60β=.Set the DCbias at 50mA. 50 ,inR=Ω3,aRK=Ω6bRKand the bias supply voltage is 10V. When the light source is on, its voltage drop is 1.8V. inVinRbRaRcRCdcVcebBIcIEILEDa)Compute the value of the emitter resistance eR. b)Compute the collector-emitter voltage at the Q point. c)Figure out the maximum modulation factor this circuit can provide. Problem 2: The LED whose output characteristic is shown in the below figure is used in a two-channel frequency-division-multiplexed system. The LED total harmonic distortion is measured as 25 dB when a sinusoidal current with a 50 mA peak is applied. The bias current is set at 50 mA. The AM modulation of each subcarrier is 50%. The intensity modulation is 100%. The subcarriers are at 1 MHz and 2 MHz and have equal peak currents. The information is a1000 Hz tone for both
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