Semi Conductors Objectives Part 05
81 . The holes diffuse from P region to the N region in a PN-junction diode because there is greater concentration of holes in the P-region as compared to N-region.
82 . Ina semi-conductor diode, the barrier offers opposition to majority carriers in both regions.
83 . For a PN diode the number of minority carriers crossing the junction mainly depends on rate of thermal generation of electron hole pairs.
84 . The V-I characteristics of a semiconductor diode is shown in Fig.9. From this figure it can be concluded that the diode is silicon diode.
85 . If too large current passes through the diode excessive heat may damage the diode.
86 . 10 A could be the maximum current rating of junction diode.
87 . When reverse bias is applied to a junction diode potential barrier is raised.
88 . For a PN-Junction diode, the current in reverse bias may be few micro or Nano amperes.
89 . Figure A represents an ideal diode characteristic.
90 . Potential barrier is decreased when forward bias applied to a junction diode.
91 . When reverse bias exceeds a certain value avalanche breakdown in a semi-conductor diode occurs.
Question 92 and 93 refer to data given
The turns ratio of a transformer used in half wave rectifier is 10: 1. The primary is connected to the power mains, 220 V, 50 Hz.
92 . If the diode resistance in forward bias is zero, the dc voltage across the load will be nearly 10 V.
93 . The peak inverse voltage of the diode will be 31V.
94 . Bridge rectifier needs four diodes.
95 . The ripple factor for a half wave rectifier is 1.21.
96 . The ripple factor for a full wave rectifier is 0.482.
97 . Maximum rectification efficiency for a half wave rectifier is 40.6%.
98 . The maximum rectification efficiency in case of full wave rectifier is 81.2%.
99 . A full wave bridge rectifier is supplied voltage at 50 Hz The lowest ripple frequency will be 100Hz.
100 . For signal diodes the PIV rating is usually in the range 30V to 150V.