EXERCISES . In an n-type silicon, which of the following statement is true: (a) Electrons are majority carriers and trivalent atoms are the dopants. (b) Electrons are minority carriers and pentavalent atoms are the dopants. (c) Holes are minority carriers and pentavalent atoms are the dopants.
(d) Holes are majority carriers and trivalent atoms are the dopants. . Which of the statements given in Exercise . is true for p-type semiconductos.
. Carbon, silicon and germanium have four valence electrons each. These are characterised by valence and conduction bands separated by energy band gap respectively equal to ( E g ) C , ( E g ) Si and ( E g ) Ge . Which of the following statements is true?
(a) ( E g ) Si < ( E g ) Ge < ( E g ) C (b) ( E g ) C < ( E g ) Ge > ( E g ) Si (c) ( E g ) C > ( E g ) Si > ( E g ) Ge (d) ( E g ) C = ( E g ) Si = ( E g ) Ge . In an unbiased p-n junction, holes diffuse from the p-region to n-region because (a) free electrons in the n-region attract them. (b) they move across the junction by the potential difference. (c) hole concentration in p-region is more as compared to n-region.
(d) All the above. . When a forward bias is applied to a p-n junction, it (a) raises the potential barrier. (b) reduces the majority carrier current to zero.
(c) lowers the potential barrier. (d) None of the above. . For transistor action, which of the following statements are correct: (a) Base, emitter and collector regions should have similar size and doping concentrations.
(b) The base region must be very thin and lightly doped. (c) The emitter junction is forward biased and collector junction is reverse biased. (d) Both the emitter junction as well as the collector junction are forward biased. .
For a transistor amplifier, the voltage gain (a) remains constant for all frequencies. (b) is high at high and low frequencies and constant in the middle frequency range. (c) is low at high and low frequencies and constant at mid frequencies. (d) None of the above.
. In half-wave rectification, what is the output frequency if the input frequency is Hz. What is the output frequency of a full-wave rectifier for the same input frequency. .
For a CE-transistor amplifier, the audio signal voltage across the collected resistance of k < is V. Suppose the current amplification factor of the transistor is , find the input signal voltage and base current, if the base resistance is k < . . Two amplifiers are connected one after the other in series (cascaded).
The first amplifier has a voltage gain of and the second has a voltage gain of . If the input signal is . volt, calculate the output ac signal. .
A p-n photodiode is fabricated from a semiconductor with band gap of . eV. Can it detect a wavelength of nm?