128. Electrons can be emitted from a metal surface due to high electric field.
129. In an n type semiconductor the fermi level is 0.35 eV below the conduction band, the concentration of donor atoms is increased to three times. The new position of Fermi level will be
130. Assertion (A): In a BJT, the base region is very thick. Reason (R): In p-n-p transistor most of holes given off by emitter diffuse through the base.
131. Assertion (A): The behaviour of FET is similar to that of a pentode. Reason (R): FETs and vacuum triode are voltage controlled devices.
132. SCR can be turned on by applying anode voltage at a sufficient fast rateapplying sufficiently large anode voltageincreasing the temperature of SCR to a sufficientlyapplying sufficiently large gate current.
133. In a bipolar transistor
134. If for a silicon n-p-n transistor, the base to emitter voltage (VBE) is 0.7 V and the collector to base voltage VCB is 0.2 Volt, then the transistor is operating in the
135. The number of doped regions in a bipolar junction transistor is
136. Donor energy level is n type semiconductor is very near valence band.
137. GaAs has an energy gap 1.43 eV the optical cut off wavelength of GaAs would lie in the
138. Which of the following is basically a voltage controlled capacitance?
139. When the i-v curve of a photodiode passes through origin the illumination is
140. An n type silicon bar 0.1 cm long and 100 μm2 in cross-sectional area has a majority carrier concentration of 5 x 1020/m3 and the carrier mobility is 0.13 m0/V-s at 300k. If the charge of an electron is 1.6 x 10-19 coulomb, then the resistance of the bar is
141. The threshold voltage of a MOSFET can be lowered by using thin gate oxidereducing the substrate concentrationincreasing the substrate concentration. Of the above statement
142. In which device does the extent of light controls the conduction
143. An increase in junction temperature of a semiconductor diode
144. An air gap provided in the iron core of an inductor prevents
145. Generally, the gain of a transistor amplifier falls at high frequency due to the
146. Which of these has a layer of intrinsic semiconductor?
147. Assertion (A): When Diode used as rectifier the reverse breakdown voltage should not be exceeded. Reason (R): A high inverse voltage can destroy a p-n junction.
148. A Si sample is doped with a fixed number of group N impurities. The electron density n is measured from 4 K to 1200 k for the sample. Which one of the following is correct?
149. Assertion (A): In design of circuit using BJT, a derating factor is used. Reason (R): As the ambient temperature increases, heat dissipation becomes slower.
150. If the drift velocity of holes under a field gradient of 100 V/m is 5m/sec. Their mobility is