Section A
Q1.
(a) (i) Calculate the temperature at which silicon (Si) semiconductor tends to behave like a metal. (ii) Prove that reverse saturation current approximately doubles for every 10 °C rise in temperature in a semiconductor diode.
(b) (i) Prove that when two resistors are connected in parallel, the equivalent resistance of the combination is always smaller than that of smaller resistor. (ii) A conductor has resistance 5.4 \Omega at 20 °C and 7 \Omega at 100 °C. Determine the resistance of the conductor at 0 °C.
(c) What is 'line imperfection defect' in a crystal? How does it affect the properties of a metal?
(d) (i) Enumerate the different performance indices based on which an engineer selects an instrument. (ii) What is the SI system of units? Mention some (at least four) well-defined units maintained by the International System of Units.
(e) In the circuit shown in the figure below, I = 1 mA is a DC current and v_{\textin}(t) is a sinusoidal voltage with small amplitude : Representing the diode by its small signal resistance rd, which is a function of I, sketch the circuit for determining v0(t) and thus find out cutoff frequency fH. (Assume VT = 25 mV at room temperature)