1. Determine the value of R to operate a red LED at 15 mA. Assume that Vs = 9V and Vf=2V. Note: In class we labeled the voltage drop across the LED as VD; VD=Vf. + Vs R V 2. A 4800 mAh cell phone battery lasts for 24 hours in talk time. The nominal voltage of the battery is 3.7 V. Determine the current drawn from the battery when talking on the phone and the power rating. Assume that the cell phone is 100% efficient. 3. Sketch the the ouput signal of the circuit below measured on the resistor RL. Explain the observed waveform. Input waveform VMAX IF diode RL www