1. Calculate the dc voltage applied to the 10 ? load resistor in the circuit shown below (assume the diode threshold voltage is 0.7 V and the bulk resistance is 0 ?).

2. What value should R be in the circuit shown below to set up a diode current of 0.50 mA? (assume the diode threshold voltage is 0.7 V and the bulk resistance is 0 ?).

3. Calculate the base current entering each transistor, IB1 and IB2, and the total current gain, total, for the following circuit (assume that each transistor is made from silicon and has a VBE of 0.7 V).

4. A factory has a maximum demand of 400 kW at a lagging power factor such that 600 kVAr of reactive power has to be supplied. Consider the effect of adding capacitor banks in two stages, each drawing 200 kVAr leading. Calculate the power factor and the apparent power in each case:

(a) without capacitive load

(b) with one capacitive load of 200 kVAr

(c) with two capacitive loads of 200 kVAr totalling 400 kVAr

5. Using a summing operational amplifier, design a 3-bit digital to analogue converter (DAC). Assume the digital inputs are generated from a TTL circuit (logic 0 equal to 0 V, logic 1 equal to 5 V). The converter output should feed a speaker which has a maximum input voltage of 3.5 V. Draw a diagram of your completed circuit design and explain its operation.