In a transistor amplifier, the two ac current gains  as defined as . The relation between  is


Correct option is


We know that . Dividing both sides by , we get 






A semiconductor has an electron concentration of m–3 and a hole concentration of . Calculate its conductivity. Given : electron mobility , hole mobility 


In a pure Ge sample at room temperature the electron and hole concentration is each equal to . It is doped with indium, 1 indium atom is added for 106 Ge atoms. Find the conductivity of doped Ge. The concentration of Ge atoms in the sample is . Given :    



Find the number density (concentration) of donor atoms to be added to an intrinsic germanium semiconductor to produce an n-type semiconductor of conductivity . The mobility of electron in n-type germanium is 3900 cm2V–1s–1. Neglect the contribution of holes to the conductivity.


A semiconductor is known to have an electron concentration of  and a hole concentration of . Is the semiconductor n-type or p-type? What is the resistivity of the sample if the electron mobility is 23,000 cm2V–1s–1 and hole mobility is 100 cm2V–1s–1.


The electrical conductivity of  a semiconductor inceases when electromagnetic radiation of wavelength shorter than 2480 nm is incident on it. Find the band gap for the semiconductor. Given :



At absolute zero of temperature, the electrical conductivity of a pure semiconductor is


In pure silicon at 300 K the electron and hole concentration is each equal to . When doped with indium, the hole concentration increases to . What is the electron concentration in doped silicon?


In a transistor circuit, the collector current is 50 mA and the base current is 1 mA. The current gain  is


In a transistor circuit, the collector current is 9.8 mA and the base current is 10 mA. The current gain  is 


In a transistor, a change of 8.0 mA in the emitter current produces a change of 7.8 mA in the collector current. What change in the base current is necessary to produce the same change in the collector current?