A Si Diode (p-n junction) Is Connected To A Resistor R and A Biasing Battery Of Variable Voltage VB. Assume That Diode Requires A Maximum Current Of 1 MA To Be Above The Knee Point (0.7 V) Of Its V-i characteristic Curve. Also Assume That The Voltage V across The Diode Is Independent Of Current Above The Knee Point. If VB = 5 V, What Should Be The Maximum Value Of R so That The Voltage V is Above The Knee-point Voltage?                                                                      

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Question

A Si diode (p-junction) is connected to a resistor R and a biasing battery of variable voltage VB. Assume that diode requires a maximum current of 1 mA to be above the knee point (0.7 V) of its V-i characteristic curve. Also assume that the voltage V across the diode is independent of current above the knee point. If VB = 5 V, what should be the maximum value of R so that the voltage V is above the knee-point voltage?   

                                                                  

Solution

Correct option is

Let VR and V be the voltages across the resistor R and the diode respectively. Then       

         

  

              .

For R to be maximum (Rmax), the current i should be minimum . Thus, by Ohm’s law

           

  

                   

                   

                 .

SIMILAR QUESTIONS

Q1

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Q7

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Q8

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Q9

A forward-biased p-n junction diode has a potential drop of 0.5 V which is assumed to be independent of current. The current in excess of 10 mA through the diode produces so much heating that burns the diode. If we have a 1.5 V battery to bias the diode, resistor must be used in series with the diode so that the maximum current does not exceed 5 mA?   

Q10

In the circuit (a), calculate the current in the  resistance. Assume that each diode is of silicon (Si) and its potential barrier is 0.7 volt, and forward-resistance is .