136. The number of p-n junctions in a thyristor is—

1. 1. 1

   
   
   

   2. 2

   
   
   

   3. 3

   
   
   

   4. 4

   
   
   

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   NA

   Correct Option: C

   NA

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137. In the circuit of given Fig. the diode states at the extremely large negative value of the input voltage v_i are—
     
     
     

1. 1. D1 off, D2 off

   
   
   

   2. D1 on, D2 off

   
   
   

   3. D1 off, D2 on

   
   
   

   4. D1 on, D2 on

   
   
   

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   NA

   Correct Option: B

   NA

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138. Fig. shows an electronic voltage regulator. The zener diode may be assumed to require a minimum current of 25 mA for satisfactory operation. The value of R required for satisfactory operation is…… ohm.
     
     
     

1. 1. 80

   
   
   

   2. 40

   
   
   

   3. 20

   
   
   

   4. None of these
      

   
   
   

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   NA

   Correct Option: A

   NA

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139. 13. In the circuit of Fig. the 5V zener diode requires a minimum current of 10 mA. For obtaining a regulated output of 5 V, the maximum permissible load current I_L is ……… and the minimum power rating of zener diode is …….
     
     
     

1. 1. 40 mA, 0·05 W

   
   
   

   2. 20 mA, 0·05 W

   
   
   

   3. 40 mA, 0·5 W

   
   
   

   4. 20 mA, 0·5 W

   
   
   

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   NA

   Correct Option: A

   NA

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140. The circuit in Fig. shows zener-regulated dc power supply. The zener diode is ideal. The minimum value of R_L down to which the output voltage remains constant is—
     
     
     

1. 1. 27 Ω

   
   
   

   2. 45 Ω

   
   
   

   3. 15 Ω

   
   
   

   4. 24 Ω
      

   
   
   

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   NA

   Correct Option: B

   NA

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