Question

Consider the following statements S₁ and S₂ 

S₁: Theβ  of a bipolar transistor reduces if the base width is increased. 

S₂: The β of a bipolar transistor increases if the doping concentration in the base is increased. Which one of the following is correct? 

(a) S₁ is FLASE and S₂ is TRUE 

(b) Both S₁ and S₂ are TRUE 

(c) Both S₁ and S₂ are FLASE 

(d) S₁ TRUE and S₂ is FALSE

Answer 1

Correct option (d) S₁ TRUE and S₂ is FALSE

Explanation :

Note the relation between α andβ   current gains

 β=i_c /i_b=α /1--α  

If base width of transistor increases, recombination in base region increases, and thus α decreases and hence β decreases. 

Thus S₁ is true

 If doping of base region increases, then recombination is base increases and α decreases thereby decreasing β 

thus S₂ is true false