Transistors Question & AnswersNovember 29, 2021 By WatElectronics This article lists 100 Transistors MCQs for engineering students. All Transistors Questions & Answers given below include a hint and wherever possible link to the relevant topic. This is helpful for users who are preparing for their exams, interviews, or professionals who would like to brush up their fundamentals on the Transistors topic which is core in Electronics & Electrical Engineering.In most electrical and electronic devices, transistors play a key role. Transistors were developed in 1947 by three American physicists namely Walter Brattain, William Shockley & John Bardeen. So transistors are considered as one of the most essential inventions within science history. Transistors are semiconductor devices that can be used for conducting as well as insulating electric voltage or current. So, they can be used as an amplifier and a switch to control otherwise regulate the electronic signal flow.The NPN and PNP transistors both are bipolar transistors that have two junctions. The emitter and collector of an NPN transistor are made up of N-type semiconductors, and the base is made up of P-type semiconductors whereas the base of PNP transistors is made up of N-type semiconductors. The emitter and collector of a PNP transistor are made up of a P-type semiconductor. When the BJT is used for the amplification of the signal then it can be operated in an active region. In a BJT common emitter configuration, the emitter terminal is common between input and output. In three regions BJT can operate are active, cut-off, and saturation regions.The bipolar junction transistor is categorized into two types they are NPN and PNP transistors. In a bipolar junction transistor, the gain is characterized by the voltage gain, the terminals are not interchangeable and the emitter is heavily doped.1). The transistors are divided broadly into ….types? 2 3 4 5 HintThey are BJTs, FETs & IGBTs. 2). The minority concentration of transistor under open circuit condition is-------? Zero Constant Infinite None of the above. HintThe minority concentration will constant and equal to thermal equilibrium values of respective charge carrier in the emitter, base and collector regions..3). In the active region the emitter-base junction is --------biased and base-collector junction is---------biased? Reversed biased, Forward biased Forward biased, Forward biased Reversed biased, Reversed biased Forward biased, Reverse biased Hintit is forward and reverse biased.4). Due to forward biasing of emitter-base junction ----------are induced into the base? Minority carriers Majority carriers All the charge carriers Only electrons. HintThe lowering of the emitter-base barrier leads to injection of minority carriers from the emitter to the base region as well as from base to the emitter region..5). The heavily doped region of the transistor is-----? Emitter Collector Both emitter and collector Only collector HintIn order to have a sufficient amount of carrier that can reach the collector the emitter is highly doped.6). The collector current IC and emitter current IE have---? Same sign in both n-p-n and p-n-p transistors. Opposite sign in both n-p-n and p-n-p transistors. No sign None of the above. HintThey have reverse signs.7). Sign of the emitter current in positive in---? p-n-p transistor. n-p-n transistor. Both a and b Only b HintThe majority charge carriers in this transistor is holes.8). In the active region, collector current depends upon----? Collector voltage. Emitter voltage. Emitter current. None of the above. HintThe current at emitter terminal.9). The technique used for manufacturing of transistors---? Epitaxial technique. Alloy technique Diffusion technique. All of the above. HintIt uses all the techniques like epitaxial,alloy and diffusion. 10). When the base region is common to both input and output circuits, the configuration is called-----? Common Emitter. Common Base. Common Collector. Open circuit. HintThis is a CB configuration.11). The width of the depletion region -------------with the magnitude of the reverse voltage? Increases Decreases Remains constant None of these HintThis is because the emitter junction is forward biased and collector junction is reverse biased..12). According to Early effect the effective base width changes due to--------? Emitter voltage. Base voltage. Collector voltage. Collector current. HintThe voltage at collector terminal.13). During the punch-through phenomenon, the effective base width is--------? Infinite Steady Zero None of the above. HintThere is no change in its width.14). The voltage level below which the emitter current is very small is called------? Junction voltage. Threshold voltage. Output voltage. All of the above. HintThe voltage at gate terminal at which the device begins to switch on.15). In common base configuration, the region where both emitter and collector junctions are forward biased is known as----? Saturation region Active region. Cut-off region. None of the above. HintIn this region, transistor works like a switch.16). In common-emitter configuration the independent variables are----? Input current and input voltage. Input current and output current. Input current and output voltage. Input voltage and output voltage. HintThe i/p current & o/p voltages are independent variables.17). The dependent variables in the common-emitter configuration are---? Input voltage and output current. Input current and output voltage. Input current and output current. Input voltage and output voltage HintThe i/p voltage & o/p current are dependent variables.18). In common emitter configuration, the input characteristics, when collector shorted to emitter and emitter is forward biased are similar to---? Forward biased diode. Reverse biased diode. Junction diode All of the above. HintOnce the voltage across a diode allows the natural current flow.19). The reverse collector saturation current ICBO of common emitter configuration----------for every 100C increase in temperature? Decreases Remains the same. Doubles. Goes infinite HintIt is twice at the present temperature.20). The generalized transistor expression, when reverse saturation current ICO and VC are given? Ic= αIE+ICO (1+e^(VC⁄VT )) Ic= -αIE+ICO (1+e^(VC⁄VT )) Ic= -αIE+ICO (1-e^(VC⁄VT )) Ic= -αIE-ICO (1-e^(VC⁄VT )) HintIt is Ic= -αIE+ICO (1-e^(VC⁄VT ))21). When voltage amplification is greater than unity the transistor acts as? Oscillator. Amplifier. Diode Transformer. HintWhen load resistance is applied in series to the collector supply voltage the amplification is given as A = (∆V_L)⁄(∆V_i ) where ∆V_L is the change in output voltage, ∆V_i is the change in input voltage.22). In common base configuration, the output voltage is ----? Collector to base voltage VCB Emitter to base voltage VEB Base voltage VB None of the above. HintIn common base configuration the output voltage is the collector to base voltage.23). In common base configuration, the input voltage VEB is the function of? Input current and output current. Input current and output voltage. Output current and input voltage None of the above. HintIn common base configuration VEB = ∅(VCB,IE).24). The approximate threshold voltage Vγ values for germanium and silicon transistors are….respectively.? 0.1 V, 0.5V 0.5V, 0.1V 0.72V,0.1V 0.72, 0.5V HintThey are 0.1 volts & 0.5 volts.25). When input voltage VEB is constant, the increase in collector voltage causes Emitter current to-----? Decrease. Become infinity. zero. Increases HintDue to Early effect, when collector voltage is increased Emitter current increases..Transistors MCQs for Exams26). When IE = 0 , the collector current IC =? Reverse saturation current ICO. Base current IB. Zero. Infinite. HintWhen the input current is zero, the current in the circuit will be due to movement of carriers from collector to the base region, causing reverse saturation current. 27). For p-n-p transistor Ic and Ico are---? Both Positive. Both Negative. Positive and negative simultaneously. Negative and positive simultaneously. HintThey are not possitive.28). The large signal current gain α of a common base transistor, when collector current IC= ICO and emitter current IE = 0 are given------ IC/IE (IC-ICO)/(IE-0) -(IC-ICO)/(IE-0) (IC-ICO)/IE HintThe large signal current gain is defined as the ratio of negative of collector current increment from cut-off to the emitter current change from the cutoff..29). In common emitter configuration, if current gain β is defined as β=α/(1-α) the collector current is given as? IC=(1+β) ICO+βIB IC=(1-β) ICO+βIE IC=(1+β) IEB+βIB IC=(1-β) IEB+βIB HintThe collector current is IC=(1+β) ICO+βIB.30). In common collector configuration, the input current is? Base current. Emitter current. Collector current. zero HintIn common collector, configuration collector is a common terminal and Base region is used for input while emitter region as output.31). Transistors are formed by the back-to-back connection of? Two PN junction diodes. Three PN junction diodes. Two p-type regions. Two n-type regions. HintAccording to Ebers-Mall model transistors are formed when two ideal PN junction diodes are placed back-to-back.32). Commonly used transistor configuration is? CE configuration. CB configuration. CC configuration. Both b and c. HintIt is a common emitter configuration. Please refer to this link to know more about Transistor Configuration33). Based on the usage in a circuit, transistors are classified into…types? 2 3 4 5 HintThey are BJTs and FETs.34). What is a transistor? Insulator Semiconductor Device Filter Voltage controlled device HintThe component which relies on the semiconductor material’s properties.35). A transistor has ….PN junctions? 2 3 4 5 HintA transistor is formed by connecting 2 diodes end-to-end.36). How many depletion layers are there in a transistor? 2 3 4 5 HintThey are base emitter and collector base.37). The doping of a transistor can be done…..? Lightly Heavily Medium Very low HintTransistors are doped not heavily.38). The large size of the terminal in a transistor is…? Base Emitter Collector CE junction HintThis terminal has the larger electrical supply.39). In PNP, the majority charge carriers are? Electrons Holes Protons Nuetrons HintThese are minority charge carriers in NPN type transistor.40). In NPN, the majority charge carriers are? Electrons Neutrons Holes Protons HintThese are minority charge carriers in PNP type transistor.41). What is the full form of BJT? Bi-Junction Transistor Base Junction Transistor Bipolar Junction Transistor Blue Junction Transistor HintThis transistor includes two types of semiconductor materials. Please refer to this link to know more about Bipolar Junction Transistor42). The material used to made a transistor is? Silicon Iron Copper Germanium HintThe chemical formula for this element is ‘Si’43). The purpose of transistor biasing in an amplifier circuit is….? Fix the current amplification value To check the transistor is saturated or not To check the performance of transistor To restrict the flow of current HintThe flow of current can be amplified.44). The transistor’s input impedance is…? Low High Medium Very less HintThe input impedance of the transistor is not high.45). Which of the following is correct in a transistor? IC = IB+IE IB = IC+IE IE = IC+IB IE = IC-IB HintThe emitter current is equal to the collector and base current.46). The output impedance of a transistor is…..? Low Medium High Very high HintThe output impedance is not low.47). If a DC current gain of a NPN transistor (Beta) value is 200 and calculate the IB value necessary for switching a 4mA of switching load? 20 uA 25 uA 30 uA 35 uA HintBy using the formula IB = IC/Beta.48). If a NPN transistor has base voltage (Vb) is 10V, Rb is 100 kilo ohms, calculate the base current? 80 uA 90 uA 93 uA 95 uA HintBy using the formula IB = VB-VBE/RB.49). Which of the following configuration is used in most of the transistors? CC CE CB None of the above HintIn this configuration, base is the input terminal50). In which of the following configuration is used highest to connect the transistor’s input impedance? CC CE CB None of the above HintIn this configuration, the collector terminal is common for both the i/p & o/p circuits.Transistors MCQs for Interviews51). In which of the following is used highest to connect the transistor’s output impedance? CC CE CB None of the above HintIn this configuration, base terminal is common to emitter & collector.52). In a CB configuration, the phase difference among the i/p & o/p voltages is…? 0 degrees 90 degrees 180 degrees 270 degrees HintIt is equal to 32 degrees Fahrenheit.53). When the transistor’s temperature increases then the resistance at BE terminal…? Increases Decreases Stable Completely reduces HintThe resistance at BE completely depends on temperature54). In CC configuration, the value of connected voltage gain is…? 1 < 10 > 10 < 1 HintThe voltage gain value is below 1.55). BC147 transistor is made with …material? Cu Si Ge Fe HintIt is a silicon material.56). The signal in a transistor is transferred from …resistance to …? Low to high High to low High to high Low to Low HintThe signal in a transistor can be transmitted from low to high resistances.57). The function of heat sink in a transistor is…? It enhances the forward current. It decreases the forward current It protects the transistor It prevents increase in extra current. HintHeat sink is used to protect the transistor from excessive current.58). The operation of transistors in a digital circuit is in …region? Breakdown Active Linear Saturation & Cutoff HintThey operate in both the regions.59). When the current ratio IC/IE<1, then it is known as….? Alpha Beta Omega Theta HintIt is the relationship of output current to the input current.60). The function of emitter resistor in a CE configuration is…? Controlling current Stabilization Protection Reduce the temperature HintThe procedure of making the working point independent of changes within temperature.61). Which of the following transistors are square law devices? BJTs FETs MOSFETs UJTs Hint These are called as field effect transistors.62). The FET provides….? Short circuit in between i/p & o/p High amount of isolation between i/p & o/p Less amount of isolation between i/p & o/p It controls the current flow. HintIt provides isolation for input and output.63). The transistor name is derived from….? Transfer run Ten resistor Transfer resistor Tran resistor HintIt means the resistance is changed.64). The bandwidth gain of FET with respect to BJT is….? Low Equal High Very low HintIt is not high as compared to BJT.65). The collector current in a transistor can be controlled through…? Base current Collector voltage Base resistance Base voltage HintThis current is 1% of collector or emitter current.66). If a 3mV signal generates a 3V output, then calculate the voltage gain.? 1000 100 30 3000 HintThe voltage gain can be calculated by Av = Vout/Vin => 3/3 * 0.001V.67). The current ratio of a beta is…? IC/IE IB/IC IE/IB IC/IB HintIt is the ratio of collector current to the base current.68). A transistor can be used like a switching device or…? Variable resistor Tuning device Rectifier Fixed resistor Hint It is used to adjust the resistance value. Please refer to this link to know more about Transistor as a Switch69). If the alpha value is 0.5 then what is the beta value? 2 1 3 4 HintThe beta value can be calculated by beta = alpha/1-alpha70). Junction transistors are called as…? BJTs FETs MOSFETs JFETs HintIt is a bipolar junction transistor.71). Which of the following transistors are current controlled devices? FETs MOSFETs JFETs BJTs HintThese are bipolar junction transistors.72). BJTs operate in …regions? 2 3 4 5 HintThey are cut off, saturation and active.73). Which of the following transistor is a voltage controlled devices? FETs MOSFETs JFETs BJTs HintThese are known as junction field effect transistors.74). Which of the following transistor is used as a switch, resistor and amplifier? JFET BJT MOSFET FET HintIt is a simple type of FET.75). Insulated Gate FET is a….? JFET BJT MOSFET FET HintIt is a metal oxide semiconductor FET.Transistors MCQs for Quiz77). The light sensitive transistors are? Power transistors Photo transistors High frequency Small switching HintThese transistors works on light.78). Field effect transistor includes…terminals? 2 3 4 5 HintThey are source, drain and gate.79). Which of the following transistor is known as unipolar transistor? FET JFET MOSFET BJT HintThese transistors need simply the majority charge carriers to work.80). The input impedance of JFET is…? Low High Medium Very high Hint JFETs has maximum impedance. Please refer to this link to know more about Junction Field Effect Transistor81). Thermal stability of BJT is…? High Low Very high Medium HintFor BJTs, thermal stability is not high.82). In a CB configuration, IE = 1mA, IC = 0.25mA then what will be the IB value?Transistor Configuration 0.75 0.95 0.65 0.85 Hint IE = IB +IC => 1 = IB+0.25 => 1-0.2583). Identify the following transistor…? BJT MOSFET FET JFET HintIt is a metal oxide semiconductor FET.84). Identify the following transistor's symbol.FET Symbol BJT MOSFET FET JFET HintIt is a field effect transistor.85). In high frequency applications, which of the following transistor is used? FET BJT MOSFET Heterojunction Bipolar Transistor HintIt is a type of BJT.86). Which of the following transistors are used in high speed ICs? FET Ballistic Transistors MOSFET Heterojunction Bipolar Transistor HintThese transistors use electromagnetic forces87). Which of the following transistors contain metal part of the MOSFET? EOSFET Ballistic Transistors FET Heterojunction Bipolar Transistor HintThese transistors detect neuronal activity.88). Which transistors work on quantum tunneling principle? EOSFET QFETs FET Heterojunction Bipolar Transistor HintThese transistors characterize through extremely high speed operation.89). ISFET stands for? Ion-sensitive FET Input sensitive FET Input switch FET Impedance sensitive FET Hint These transistors use ion concentration within the solution to change the quantity of current.90). The transistor used in environmental monitoring & biomedicine field is? ISFET MOSFET IGBT JFET Hint This is a Ion-sensitive FET.91). The transistor which uses the quantum tunneling principle is? ISFET TFET IGBT JFET HintThese transistors are used in digital circuits.92). The double gate transistors are? ISFET TFET IGBT FinFETs HintIts effective channel width can be determined through the thin Silicon (Si)‘fin’.93). What is the full form of the HEMT? High Energy Mobility Transistor High Electron Mobility Transistor High Electron Metal Transistor High Energy Metal Transistor HintThese transistors are characterized through the hetero-junction present.94). Schottky Transistor is also called as? Schottky-barrier Transistor Schottky-Clamped Transistor ISFET JFET HintThese transistors avoid saturation.95). Trench-structure based transistor is? MOSFET UMOS FET ISFET JFET HintThese transistors are similar to VMOS except the shape.96). In which of the transistor, nitrate oxide is used as insulating layer? MOSFET UMOS FET MNOS JFET HintThis is a Metal Nitride Oxide Semiconductor..97). Which of the following transistor has fast turn-off capacity? FREDFETs UMOS FET MNOS JFET HintThis is a Fast Reverse or Fast Recovery Epitaxial Diode FETs98). Which of the device is used to test a transistor? Multimeter Digital meter Ohmmeter VU meter HintThis device is used for testing purpose.99). In which year, Shockley launched the improved BJT? 1948 1945 1951 1958 HintIt is introduced in from 1947 to 1949.100). In analog & digital circuits, which of the transistor is used? FET MOSFET JFEET IGBT HintThis transistor is also known “Insulated Gate Field Effect Transistor”. Time is Up! Time's up
