
question_answer1) A silicon speciman is made into a Ptype semiconductor by dopping, on an average, one Indium atom per \[5\times {{10}^{7}}\]silicon atoms. If the number density of atoms in the silicon specimen is \[5\times {{10}^{28}}\text{atoms}/{{m}^{3}}\] then the number of acceptor atoms in silicon per cubic centimetre will be [MP PMT 1993, 2003]
A) \[2.5\times {{10}^{30}}atoms/c{{m}^{3}}\] done
clear
B) \[1.0\times {{10}^{13}}atoms/c{{m}^{3}}\] done
clear
C) \[1.0\times {{10}^{15}}atoms/c{{m}^{3}}\] done
clear
D) \[2.5\times {{10}^{36}}atoms/c{{m}^{3}}\] done
clear
View Solution play_arrow

question_answer2) The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature [IITJEE 1995; DPMT 2004]
A) Decreases exponentially with increasing band gap done
clear
B) Increases exponentially with increasing band gap done
clear
C) Decreases with increasing temperature done
clear
D) Is independent of the temperature and the band gap done
clear
View Solution play_arrow

question_answer3) The typical ionisation energy of a donor in silicon is [IITJEE 1992]
A) \[10.0\,eV\] done
clear
B) \[1.0\,eV\] done
clear
C) \[0.1\,eV\] done
clear
D) \[0.001\,eV\] done
clear
View Solution play_arrow

question_answer4) In PNjunction diode the reverse saturation current is \[{{10}^{5}}\]amp at\[27{}^\circ C.\] The forward current for a voltage of \[0.2volt\] is [MP PMT 1993]
A) \[2037.6\times {{10}^{3}}amp\] done
clear
B) \[203.76\times {{10}^{3}}amp\] done
clear
C) \[20.376\times {{10}^{3}}amp\] done
clear
D) \[2.0376\times {{10}^{3}}amp\] \[[\exp (7.62)=2038.6,\,K=1.4\times {{10}^{23}}J/K]\] done
clear
View Solution play_arrow

question_answer5) When a potential difference is applied across, the current passing through [IITJEE 1999]
A) An insulator at \[0K\] is zero done
clear
B) A semiconductor at \[0K\] is zero done
clear
C) A metal at \[0K\] is finite done
clear
D) A PN diode at \[300K\] is finite, if it is reverse biased done
clear
View Solution play_arrow

question_answer6) A 2V battery is connected across the points A and B as shown in the figure given below. Assuming that the resistance of each diode is zero in forward bias and infinity in reverse bias, the current supplied by the battery when its positive terminal is connected to A is [UPSEAT 2002]
A) 0.2 A done
clear
B) 0.4 A done
clear
C) Zero done
clear
D) 0.1 A done
clear
View Solution play_arrow

question_answer7) In the circuit, if the forward voltage drop for the diode is 0.5V, the current will be [UPSEAT 2003]
A) 3.4 mA done
clear
B) 2 mA done
clear
C) 2.5 mA done
clear
D) 3 mA done
clear
View Solution play_arrow

question_answer8) A Ptype semiconductor has acceptor levels 57 meV above the valence band. The maximum wavelength of light required to create a hole is (Planck?s constant h = \[6.6\times {{10}^{34}}\]Js) [MP PET 1995]
A) \[57\,{AA}\] done
clear
B) \[57\times {{10}^{3}}\,{AA}\] done
clear
C) \[217100\,{AA}\] done
clear
D) \[11.61\times {{10}^{33}}\,{AA}\] done
clear
View Solution play_arrow

question_answer9) Current in the circuit will be [CBSE PMT 2001]
A) \[\frac{5}{40}A\] done
clear
B) \[\frac{5}{50}A\] done
clear
C) \[\frac{5}{10}A\] done
clear
D) \[\frac{5}{20}A\] done
clear
View Solution play_arrow

question_answer10) The diode used in the circuit shown in the figure has a constant voltage drop of 0.5 V at all currents and a maximum power rating of 100 milliwatts. What should be the value of the resistor R, connected in series with the diode for obtaining maximum current [CBSE PMT 1997]
A) 1.5 W done
clear
B) 5 W done
clear
C) 6.67 W done
clear
D) 200 W done
clear
View Solution play_arrow

question_answer11) For a transistor amplifier in common emitter configuration for load impedance of 1 kW (hfe = 50 and hoe = 25 mA/V) the current gain is [AIEEE 2004]
A) ? 5.2 done
clear
B) ? 15.7 done
clear
C) ? 24.8 done
clear
D) ? 48.78 done
clear
View Solution play_arrow

question_answer12) In the following common emitter configuration an NPN transistor with current gain b = 100 is used. The output voltage of the amplifier will be [AIIMS 2003]
A) 10 mV done
clear
B) 0.1 V done
clear
C) 1.0 V done
clear
D) 10 V done
clear
View Solution play_arrow

question_answer13) In semiconductor the concentrations of electrons and holes are 8 ? 1018/m3 and 5 ? 1018/m respectively. If the mobilities of electrons and hole are 2.3 m2/voltsec and 0.01 m2/voltsec respectively, then semiconductor is
A) Ntype and its resistivity is 0.34 ohmmetre done
clear
B) Ptype and its resistivity is 0.034 ohmmetre done
clear
C) Ntype and its resistivity is 0.034 ohmmetre done
clear
D) Ptype and its resistivity is 3.40 ohmmetre done
clear
View Solution play_arrow

question_answer14) A sinusoidal voltage of peak value 200 volt is connected to a diode and resistor R in the circuit shown so that half wave rectification occurs. If the forward resistance of the diode is negligible compared to R the rms voltage (in volt) across R is approximately
A) 200 done
clear
B) 100 done
clear
C) \[\frac{200}{\sqrt{2}}\] done
clear
D) 280 done
clear
View Solution play_arrow

question_answer15) The junction diode in the following circuit requires a minimum current of 1 mA to be above the knee point (0.7 V) of its IV characteristic curve. The voltage across the diode is independent of current above the knee point. If VB = 5 V, then the maximum value of R so that the voltage is above the knee point, will be
A) 4.3 kW done
clear
B) 860 kW done
clear
C) 4.3 W done
clear
D) 860 W done
clear
View Solution play_arrow

question_answer16) In the circuit given below, V(t) is the sinusoidal voltage source, voltage drop VAB(t) across the resistance R is [IIT 1993]
A) Is half wave rectified done
clear
B) Is full wave rectified done
clear
C) Has the same peak value in the positive and negative half cycles done
clear
D) Has different peak values during positive and negative half cycle done
clear
View Solution play_arrow

question_answer17) The peak voltage in the output of a halfwave diode rectifier fed with a sinusoidal signal without filter is 10 V. The dc component of the output voltage is [CBSE PMT 2004]
A) \[10/\sqrt{2}\,V\] done
clear
B) 10/p V done
clear
C) 10 V done
clear
D) 20/p V done
clear
View Solution play_arrow

question_answer18) A transistor is used as an amplifier in CB mode with a load resistance of 5 k W the current gain of amplifier is 0.98 and the input resistance is 70 W, the voltage gain and power gain respectively are [Pb. PET 2003]
A) 70, 68.6 done
clear
B) 80, 75.6 done
clear
C) 60, 66.6 done
clear
D) 90, 96.6 done
clear
View Solution play_arrow

question_answer19) The Bohr radius of the fifth electron of phosphorus (atomic number = 15) acting as dopant in silicon (relative dielectric constant = 12) is
A) 10.6 A done
clear
B) 0.53 A done
clear
C) 21.2 A done
clear
D) None of these done
clear
View Solution play_arrow

question_answer20) In the following circuits PNjunction diodes D1, D2 and D3 are ideal for the following potential of A and B, the correct increasing order of resistance between A and B will be (i) ? 10 V, ? 5V (ii) ? 5V, ? 10 V (iii) ? 4V, ? 12V
A) (i) < (ii) < (iii) done
clear
B) (iii) < (ii) < (i) done
clear
C) (ii) = (iii) < (i) done
clear
D) (i) = (iii) < (ii) done
clear
View Solution play_arrow

question_answer21) The circuit shown in following figure contains two diode D1 and D2 each with a forward resistance of 50 ohms and with infinite backward resistance. If the battery voltage is 6 V, the current through the 100 ohm resistance (in amperes) is [IITJEE 1997]
A) Zero done
clear
B) 0.02 done
clear
C) 0.03 done
clear
D) 0.036 done
clear
View Solution play_arrow

question_answer22) Find VAB [RPMT 2000]
A) 10 V done
clear
B) 20 V done
clear
C) 30 V done
clear
D) None of these done
clear
View Solution play_arrow

question_answer23) A diode is connected to 220 V (rms) ac in series with a capacitor as shown in figure. The voltage across the capacitor is
A) 220 V done
clear
B) 110 V done
clear
C) 311.1 V done
clear
D) \[\frac{220}{\sqrt{2}}V\] done
clear
View Solution play_arrow

question_answer24) A potential difference of 2V is applied between the opposite faces of a Ge crystal plate of area 1 cm2 and thickness 0.5 mm. If the concentration of electrons in Ge is 2 ? 1019/m3 and mobilities of electrons and holes are \[0.36\frac{{{m}^{2}}}{volt\sec }\] and \[0.14\frac{{{m}^{2}}}{volt\sec }\] respectively, then the current flowing through the plate will be
A) 0.25 A done
clear
B) 0.45 A done
clear
C) 0.56 A done
clear
D) 0.64 A done
clear
View Solution play_arrow

question_answer25) The contribution in the total current flowing through a semiconductor due to electrons and holes are \[\frac{3}{4}\] and \[\frac{1}{4}\] respectively. If the drift velocity of electrons is \[\frac{5}{2}\] times that of holes at this temperature, then the ratio of concentration of electrons and holes is
A) 6 : 5 done
clear
B) 5 : 6 done
clear
C) 3 : 2 done
clear
D) 2 : 3 done
clear
View Solution play_arrow

question_answer26) Ge and Si diodes conduct at 0.3 V and 0.7 V respectively. In the following figure if Ge diode connection are reversed, the valve of V0 changes by [Based on Roorkee 2000]
A) 0.2 V done
clear
B) 0.4 V done
clear
C) 0.6 V done
clear
D) 0.8 V done
clear
View Solution play_arrow

question_answer27) In the circuit shown in figure the maximum output voltage V0 is
A) 0 V done
clear
B) 5 V done
clear
C) 10 V done
clear
D) \[\frac{5}{\sqrt{2}}V\] done
clear
View Solution play_arrow

question_answer28) In the following circuit find I1 and I2
A) 0, 0 done
clear
B) 5 mA, 5 mA done
clear
C) 5 mA, 0 done
clear
D) 0, 5 mA done
clear
View Solution play_arrow

question_answer29) For the transistor circuit shown below, if b = 100, voltage drop between emitter and base is 0.7 V then value of VCE will be
A) 10 V done
clear
B) 5 V done
clear
C) 13 V done
clear
D) 0 V done
clear
View Solution play_arrow

question_answer30) In NPN transistor, 1010 electrons enters in emitter region in 10?6 sec. If 2% electrons are lost in base region then collector current and current amplification factor (b) respectively are
A) 1.57 mA, 49 done
clear
B) 1.92 mA, 70 done
clear
C) 2 mA, 25 done
clear
D) 2.25 mA, 100 done
clear
View Solution play_arrow

question_answer31) The following configuration of gate is equivalent to [AMU 1999]
A) NAND done
clear
B) XOR done
clear
C) OR done
clear
D) None of these done
clear
View Solution play_arrow

question_answer32) Figure gives a system of logic gates. From the study of truth table it can be found that to produce a high output (1) at R, we must have
A) X = 0, Y = 1 done
clear
B) X = 1, Y = 1 done
clear
C) X = 1, Y = 0 done
clear
D) X = 0, Y = 0 done
clear
View Solution play_arrow

question_answer33) The combination of gates shown below produces
A) AND gate done
clear
B) XOR gate done
clear
C) NOR gate done
clear
D) NAND gate done
clear
View Solution play_arrow

question_answer34) The shows two NAND gates followed by a NOR gate. The system is equivalent to the following logic gate
A) OR done
clear
B) AND done
clear
C) NAND done
clear
D) None of these done
clear
View Solution play_arrow

question_answer35) The diagram of a logic circuit is given below. The output F of the circuit is represented by
A) \[W.(X+Y)\] done
clear
B) \[W\cdot \,(X\cdot Y)\] done
clear
C) \[W+(X\cdot Y)\] done
clear
D) \[W+(X+Y)\] done
clear
View Solution play_arrow

question_answer36) The plate current ip in a triode valve is given \[{{i}_{p}}=K{{({{V}_{p}}+\mu \,{{V}_{g}})}^{3/2}}\] where ip is in milliampere and Vp and Vg are in volt. If rp = 104 ohm, and \[{{g}_{m}}=5\times {{10}^{3}}mho,\] then for \[{{i}_{p}}=8\,mA\] and \[{{V}_{p}}=300\,volt,\] what is the value of K and grid cut off voltage [Roorkee 1992]
A) ? 6V, (30)3/2 done
clear
B) \[\,6V,\,{{(1/30)}^{3/2}}\] done
clear
C) + 6V, (30)3/2 done
clear
D) + 6V, (1/30)3/2 done
clear
View Solution play_arrow

question_answer37) The linear portions of the characteristic curves of a triode valve give the following readings [Roorkee 1985]
\[{{V}_{g}}\](volt)  0  ? 2  ? 4  ? 6 
\[{{I}_{p}}(mA)\] for \[{{V}_{p}}=150\] volts  15  12.5  10  7.5 
\[{{I}_{p}}(mA)\] for \[{{V}_{p}}=120\] volts  10  7.5  5  2.5 
The plate resistance is
A) 2000 ohms done
clear
B) 4000 ohms done
clear
C) 8000 ohms done
clear
D) 6000 ohms done
clear
View Solution play_arrow

question_answer38) The relation between dynamic plate resistance (rp) of a vacuum diode and plate current in the space charge limited region, is
A) \[{{r}_{p}}\propto {{I}_{p}}\] done
clear
B) \[{{r}_{p}}\propto I_{p}^{3/2}\] done
clear
C) \[{{r}_{p}}\propto \frac{1}{{{I}_{p}}}\] done
clear
D) \[{{r}_{p}}\propto \frac{1}{{{({{I}_{p}})}^{1/3}}}\] done
clear
View Solution play_arrow

question_answer39) The relation between Ip and Vp for a triode is \[{{I}_{p}}=(0.125{{V}_{p}}7.5)\,mA\]Keeping the grid potential constant at 1V, the value of rp will be
A) 8 kW done
clear
B) 4 kW done
clear
C) 2 kW done
clear
D) 8 kW done
clear
View Solution play_arrow

question_answer40) An alternating voltage of 141.4V (rms) is applied to a vacuum diode as shown in the figure. The maximum potential difference across the condenser will be
A) 100 V done
clear
B) 200 V done
clear
C) \[100\sqrt{2}V\] done
clear
D) \[200\sqrt{2}V\] done
clear
View Solution play_arrow

question_answer41) A metallic surface with work function of 2 eV, on heating to a temperature of 800 K gives an emission current of 1 mA. If another metallic surface having the same surface area, same emission constant but work function 4 eV is heated to a temperature of 1600 K, then the emission current will be
A) 1 mA done
clear
B) 2 mA done
clear
C) 4 mA done
clear
D) None of these done
clear
View Solution play_arrow

question_answer42) A change of 0.8 mA in the anode current of a triode occurs when the anode potential is changed by 10 V. If m = 8 for the triode, then what change in the grid voltage would be required to produce a change of 4 mA in the anode current
A) 6.25 V done
clear
B) 0.16 V done
clear
C) 15.2 V done
clear
D) None of these done
clear
View Solution play_arrow

question_answer43) The plate current in a triode is given by \[{{I}_{p}}=0.004\ {{({{V}_{p}}+10{{V}_{g}})}^{3/2}}mA\]where Ip, Vp and Vg are the values of plate current, plate voltage and grid voltage, respectively. What are the triode parametersm, rp and gm for the operating point at \[{{V}_{p}}=120\,volt\] and \[{{V}_{g}}=\,2\,volt\]?
A) 10, 16.7 kW, 0.6 m mho done
clear
B) 15, 16.7 kW, 0.06 m mho done
clear
C) 20, 6 kW, 16.7 m mho done
clear
D) None of these done
clear
View Solution play_arrow

question_answer44) A triode whose mutual conductance is 2.5 m A/volt and anode resistance is 20 kilo ohm, is used as an amplifier whose amplification is 10. The resistance connected in plate circuit will be [MP PET 1989; RPMT 1998]
A) 1 kW done
clear
B) 5 kW done
clear
C) 10 kW done
clear
D) 20 kW done
clear
View Solution play_arrow

question_answer45) In the grid circuit of a triode a signal \[E=2\sqrt{2}\cos \omega t\] is applied. If m = 14 and rp =10 kW then root mean square current flowing through \[{{R}_{L}}=12\,k\Omega \] will be
A) 1.27 mA done
clear
B) 10 mA done
clear
C) 1.5 mA done
clear
D) 12.4 mA done
clear
View Solution play_arrow

question_answer46) For a triode m = 64 and gm =1600 m mho. It is used as an amplifier and an input signal of 1V (rms) is applied. The signal power in the load of 40 kW will be
A) 23.5 mW done
clear
B) 48.7 mW done
clear
C) 25.6 mW done
clear
D) None of these done
clear
View Solution play_arrow

question_answer47) Amplification factor of a triode is 10. When the plate potential is 200 volt and grid potential is ? 4 volt, then the plate current of 4mA is observed. If plate potential is changed to 160 volt and grid potential is kept at ? 7 volt, then the plate current will be
A) 1.69 mA done
clear
B) 3.95 mA done
clear
C) 2.87 done
clear
D) 7.02 mA done
clear
View Solution play_arrow

question_answer48) On applying a potential of ? 1 volt at the grid of a triode, the following relation between plate voltage Vp (volt) and plate current \[{{I}_{p}}(\text{in }mA)\] is found \[{{I}_{p}}=0.125\,{{V}_{p}}7.5\]If on applying ? 3 volt potential at grid and 300 V potential at plate, the plate current is found to be 5mA, then amplification factor of the triode is
A) 100 done
clear
B) 50 done
clear
C) 30 done
clear
D) 20 done
clear
View Solution play_arrow

question_answer49) The slopes of anode and mutual characteristics of a triode are 0.02 mA V?1 and 1 mA V?1 respectively. What is the amplification factor of the valve [MP PMT 1990]
A) 5 done
clear
B) 50 done
clear
C) 500 done
clear
D) 0.5 done
clear
View Solution play_arrow

question_answer50) The voltage gain of the following amplifier is [AIIMS 2005]
A) 10 done
clear
B) 100 done
clear
C) 1000 done
clear
D) 9.9 done
clear
View Solution play_arrow