This semester we discussed a voltage divider circuit that can be used to provide a voltage source for a load as shown below. Let the input voltage be 10 volts and assume the load resistor can vary over a range RL = 1000 Ω. The objective of this problem is to determine values of R1 and R2 to provide a load voltage of 5.0 volts ± 10% while at the same time minimizing power consumption.
a. Write down a relationship for the load voltage in terms of the input voltage, R1, R2, and RL.
b. Determine the relationship between R1 and R2 such that the load voltage is always in the range of 5.0 volts ± 10%.
c. Determine approximate values of R1 and R2 that satisfy the constraint of part b, but also provide for minimum power consumption.
We also showed that power consumption can be reduced by introducing an active component, such as a bipolar transistor, into the circuit. The model for such a circuit is shown below.
d. When using the node method to solve this problem, we end up with 2 unknown voltages, VB and VL. Explain why.
e. Repeat parts b and c to determine R1 and R2 for the correct output voltage and minimum power consumption.