The circuit in Figure P9.58 is used to drive an LED with a voltage source. The circuit can...

The circuit in Figure P9.58 is used to drive an LED with a voltage source. The circuit can also be thought of as a current amplifier in that, with the proper

design, iD > i1 (a) Derive the expression for iD in terms of i1 and the resistors. (b) Design the circuit such that iD = 12 mA and; i1 = 1 mA for υI =5V.