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

In a pn junction dipole at a high value of reverse bias, the current rises sharply. The value of reverse bias is known as

Q2

The total current in the block is 

Q3

In a pnp transistor, the p-type crystal acts as

Q4

The current gain in a common emitter transistor is

Q5

If the input and output resistances in a common-base amplifier circuit are  respectively, what is the voltage amplification when the emitter current is 2 mA and current gain ?

Q6

When npn transistor is used as an amplifier

Q7

When a pn junction is reverse biased, the flow of current across the junction is mainly due to

Q8

The V-i characteristic of a silicon diode is given in the figure. Calculate the diode resistance in forward bias at V = +2 volt.  

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 .