Section A
Q1.
(a) Determine the values of slope K1, K2, K3 and the voltages L_ + and L_- for the amplifier and its transfer characteristics shown in the figure given below: (R1 = 30 \text k\Omega, R2 = R5 = 9 \text k\Omega, R3 = R4 = 3 \text k\Omega, Rf = 60 \text k\Omega). The diodes may be assumed to be ideal.
(b) Determine the total energy and average power of the following signal : \mathbfx(t) = \begincases 2 & -3 ≤ t ≤ 3 \\ 5-t & 3 ≤ t ≤ 5 \\ 0 & \textotherwise \endcases
(c)
Show the permissible area for the poles of a second order system which must simultaneously meet the following criteria :
(i) Maximum percent overshoot ≤ 5%
(ii) Settling time for 2% criterion ≤ 500 ms
(d) A 1000 VA, 440/220 V single-phase two-winding transformer is connected as autotransformer to supply a load at 440 V from a supply voltage of 660 V ac mains. Draw the schematic diagram of the autotransformer with proper labelling. If the full load unity power factor (pf) efficiency of the two-winding transformer is 96.2%, what will be the full-load efficiency of the autotransformer at 0.85 pf lagging ? Also find the maximum primary and secondary currents of the autotransformer.
(e)
The reverse recovery time of a diode is trr = 6 μ s, and the rate of fall of the diode current di/dt = 10 A/µs. If the softness factor SF = 0.5, Find the storage charge QRR
(i) Find the peak reverse current IRR, and
(ii) Draw the labelled reverse recovery characteristics.
