86 + Interview Questions in High Frequency Transistor in Electronic Devices & Circuits Page 1 InterviewSolution

1.	What is the value of voltage gain in the CE short circuit current frequency response model?(a) hfe × RL / hre(b) –hfe × RL / hre(c) hfe × RL / hie(d) –hfe × RL / hieThe question was posed to me in an interview.Asked question is from The CE Short Circuit Current Frequency Response in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» Right choice is (d) –HFE × RL / hie The best I can explain: The VOLTAGE gain of a common emitter (CE) amplifier can be EXPRESSED in terms of hybrid parameters in the CE SHORT CIRCUIT current frequency response model. The voltage gain is equal to -hfe × RL / hie where, RL is load resistance, hie is input resistance and -hfe is the current gain.

Discussion

2.	How do we calculate the inverse hybrid-pi conductance in low frequency H-parameters g12 of a two-port network?(a) g12 = I2 / I1(b) g12 = I1 / I2(c) g12 = V1 / V2(d) g12 = V2 / V1This question was addressed to me in my homework.My doubt stems from Hybrid PI Conductances in Low Frequency H Parameters in division High Frequency Transistor of Electronic Devices & Circuits
Answer» The correct choice is (b) g12 = I1 / I2 To EXPLAIN I would say: The inverse hybrid-pi conductance in low frequency H-parameters g12 for a two-port network is calculated by short CIRCUITING the input terminal. In this case, the CURRENT V1 is equal to zero. The parameter g12 is calculated by taking the ratio of input terminal current over output terminal current.

Discussion

3.	What is the path of the output characteristic of a CB short circuit current frequency response in the active region?(a) Linear(b) Exponential decrease(c) Exponential increase(d) ConstantI got this question in an online interview.Query is from The CB Short Circuit Current Frequency Response in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» RIGHT option is (d) Constant The explanation is: In a CB short circuit current frequency RESPONSE model, the output CHARACTERISTIC curve first increases exponentially and then remains constant. In the active REGION of working the output characteristics SHOW a constant value collector current with respect to collector base voltage.

Discussion

4.	Which of the following four hybrid parameters is used to calculate reverse voltage gain in a high frequency T model?(a) h11(b) h12(c) h21(d) h22I had been asked this question in examination.This interesting question is from The High Frequency T Model in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» RIGHT choice is (b) h12 The explanation: The hybrid parameter h12 can be calculated by open CIRCUITING the input port in a HIGH frequency T model. By doing so, we can CALCULATE h12 = V1 / V2. Since this is a ratio between two voltage UNITS, h12 is unitless. It is known as the reverse voltage gain of the circuit.

Discussion

5.	Which of the following is an independent variable in a linear analysis of a common base transistor?(a) Base current(b) Collector base voltage(c) Collector current(d) Collector emitter voltageThe question was posed to me in an international level competition.My question comes from Transistor Amplifier Response, Taking Source Resistance into Account topic in chapter High Frequency Transistor of Electronic Devices & Circuits
Answer» The correct answer is (b) Collector base voltage Easy explanation: In a linear analysis of a common base transistor, we have two independent variables. The collector base voltage is an independent variable and the collector CURRENT is the dependent variable. We can obtain IC using VCB from the CHARACTERISTIC CURVE.

Discussion

6.	How do we calculate the value of IC in the CE short circuit current frequency response model?(a) IC = hre × IB(b) IC = -hre × IB(c) IC = hfe × IB(d) IC = -hfe × IBI have been asked this question during an internship interview.My query is from The CE Short Circuit Current Frequency Response topic in section High Frequency Transistor of Electronic Devices & Circuits
Answer» The correct choice is (C) IC = hfe × IB Easy EXPLANATION: The collector current of a common emitter (CE) amplifier can be expressed in terms of HYBRID parameters in the CE SHORT circuit current frequency response model. It is expressed as the product of hfe × IB. This is the same for approximate hybrid models as well.

Discussion

7.	How many main types of alpha cutoff frequency are there in bipolar transistors?(a) 3(b) 4(c) 5(d) 6I had been asked this question in an international level competition.The origin of the question is The Alpha Cutoff Frequency topic in division High Frequency Transistor of Electronic Devices & Circuits
Answer» Right answer is (c) 5 The BEST I can explain: There are five main type of biasing circuits. They are Fixed Bias, Collector – to – BASE Bias, VOLTAGE Divider Bias, Fixed Bias with EMITTER Resistor and Emitter Bias. Each one of these have a different alpha cutoff frequency value.

Discussion

8.	Why is it essential to stabilize the operating point of a circuit?(a) Thermal runaway, power efficiency, individual variations(b) Temperature dependency of IB, individual variations, power efficiency(c) Thermal runaway, Temperature dependency of IC, individual variations(d) Temperature dependency of IC, thermal runaway, cost efficiencyThe question was asked in a job interview.Question is from The Alpha Cutoff Frequency in section High Frequency Transistor of Electronic Devices & Circuits
Answer» Correct answer is (C) Thermal runaway, Temperature DEPENDENCY of IC, individual variations Easiest explanation: It is essential to stabilize the operating point of a circuit to prevent thermal runaway, temperature dependency of IC and individual variations. Thermal runaway OCCURS because of the SELF – destruction of an unstable transistor. Temperature dependency on IC causes major variations in IE. Individual variations of parameters such as α and VBE cause huge fluctuations in IE.

Discussion

9.	Which of the following is an inference made from the linear analysis of a transistor circuit taking source resistance into account?(a) 99% of the collector current flows to the emitter(b) 99% of the emitter current flows to the collector(c) 0.99% of the collector current flows to the emitter(d) 0.99% of the emitter current flows to the collectorI had been asked this question in an internship interview.I'd like to ask this question from Transistor Amplifier Response, Taking Source Resistance into Account in chapter High Frequency Transistor of Electronic Devices & Circuits
Answer» The correct choice is (a) 99% of the collector current flows to the emitter To explain: While performing the linear ANALYSIS of a transistor circuit TAKING source resistance into account we OBSERVE that 99% of the collector current flows to the emitter. Current always flows from the collector to the emitter and not the other way around SINCE the emitter terminal is usually grounded.

Discussion

10.	What is the value of current gain in the hybrid-pi CE transistor model?(a) hfe(b) -hfe(c) hre(d) –hreThis question was posed to me by my school teacher while I was bunking the class.My doubt stems from The Hybrid PI CE Transistor Model in section High Frequency Transistor of Electronic Devices & Circuits
Answer» The correct answer is (b) -hfe For explanation I would say: The current gain of a common emitter (CE) amplifier can be expressed in terms of hybrid parameters in the hybrid-pi CE transistor MODEL. The current gain hfe is the forward TRANSFER characteristics and is USED to CALCULATE the current gain in common emitter amplifiers.

Discussion

11.	What is the voltage gain of a current gain with resistive load amplifier?(a) 1(b) β(c) ∞(d) 0I had been asked this question during an online interview.Question is from Current Gain with Resistive Load topic in section High Frequency Transistor of Electronic Devices & Circuits
Answer» Right option is (a) 1 To explain I would say: The voltage gain of a CURRENT gain with resistive LOAD amplifier configuration is ROUGHLY equal to unity. AV is approximately equal to 1. SINCE this type of amplifier focuses more towards the current gain, the voltage gain is usually maintained at unity.

Discussion

12.	What is the bias of a simplified CB short circuit current frequency response configuration?(a) Reverse biased(b) Forward biased(c) Forward and reverse biased(d) It is independent of the biasThe question was posed to me by my college professor while I was bunking the class.The origin of the question is The CB Short Circuit Current Frequency Response topic in section High Frequency Transistor of Electronic Devices & Circuits
Answer» CORRECT option is (b) Forward BIASED Best explanation: The CB short circuit current frequency RESPONSE OPERATES such that the input signal is applied to the emitter TERMINAL and the output is taken from the collector terminal. The emitter current is also the input current, and the collector current is also the output current. The base – emitter junction is forward – biased.

Discussion

13.	How do we determine the hybrid parameters h12 and h22 in a high frequency T model?(a) Short circuiting the input terminal(b) Open circuiting the input terminal(c) Short circuiting the output terminal(d) Open circuiting the output terminalI got this question in my homework.I'm obligated to ask this question of The High Frequency T Model topic in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» RIGHT option is (b) Open circuiting the input TERMINAL To elaborate: From the four hybrid parameters, to determine the value of h12 and h22 we need to open circuit the input terminal. This in TURN makes the CURRENT from the input terminal I1 equal to ZERO. It is the same procedure in a high frequency T model.

Discussion

14.	Which model is similar to the high frequency T model?(a) G model(b) Hybrid-pi model(c) Inverse G model(d) Z modelThis question was addressed to me in an internship interview.The question is from The High Frequency T Model topic in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» CORRECT answer is (B) Hybrid-pi model For explanation I would say: The Hybrid-pi model is similar to the HIGH frequency T model. The T model can use EITHER a voltage or a current as the variable that controls the current source. In the T model, the current source’s expression is either gm VBE or αIE.

Discussion

15.	What is the other name for a current gain with resistive load amplifier configuration?(a) Common collector(b) Common base(c) Common emitter(d) Amplifier circuitThe question was asked in an online interview.I'd like to ask this question from Current Gain with Resistive Load in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» CORRECT choice is (a) COMMON collector Best EXPLANATION: The current GAIN with resistive load circuit configuration is also KNOWN as the common collector configuration as it provides a high input impedance and a low output impedance. The current gain with resistive load circuit acts as a buffer stage, and in result is used in several circuits where there is a need to prevent the loading of a circuit.

Discussion

16.	How is the input impedance of a current gain with resistive load amplifier?(a) Irrelevant(b) Moderate(c) Low(d) HighI had been asked this question in a national level competition.This interesting question is from Current Gain with Resistive Load topic in division High Frequency Transistor of Electronic Devices & Circuits
Answer»

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17.	How do you calculate the dynamic input resistance of a CB short circuit current frequency response?(a) ΔVBE / ΔIC(b) ΔVBE / ΔIE(c) ΔVCB / ΔIC(d) ΔVCB / ΔIEI have been asked this question in an online interview.I would like to ask this question from The CB Short Circuit Current Frequency Response topic in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» The correct option is (B) ΔVBE / ΔIE To EXPLAIN I would say: Dynamic INPUT resistance is DEFINED as the ratio of change in emitter base voltage to the corresponding change in the emitter CURRENT. While the collector voltage is kept at a constant value. Therefore, ri = ΔVBE / ΔIE.

Discussion

18.	Where is the input measured in a CB short circuit current frequency response?(a) Collector terminal(b) Emitter terminal(c) Base terminal(d) GroundThis question was posed to me at a job interview.The origin of the question is The CB Short Circuit Current Frequency Response in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» Correct choice is (b) Emitter TERMINAL The explanation is: In the PHYSICAL model of a CB short circuit current frequency RESPONSE the input is measured at the emitter terminal of the BJT biased device. Whereas, the OUTPUT is measured across the collector terminal of the biased BJT device.

Discussion

19.	What is the value of overall current gain in the CE short circuit current frequency response model while considering RS?(a) AI × IB / IS(b) AI × IC / IS(c) AI × IS / IC(d) AI × IS / IBI had been asked this question in quiz.I'm obligated to ask this question of The CE Short Circuit Current Frequency Response in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» Right choice is (a) AI × IB / IS To explain I WOULD say: The current gain in a simplified COMMON emitter hybrid model while considering RS is calculated as the product of current gain without EXTERNAL parameters and the ratio of base current and external applied current. It is expressed as AI × IB / IS. Where, IS is the external applied current on the amplifier.

Discussion

20.	What are the disadvantages of CE short circuit gain obtained with hybrid pi model circuits?(a) Requires few resistors(b) Provides a lot of stability(c) Provides negative feedback(d) Provides positive feedbackThe question was asked in an online interview.My question is based upon The CE Short Circuit Gain Obtained with the Hybrid PI Model topic in chapter High Frequency Transistor of Electronic Devices & Circuits
Answer» CORRECT option is (C) Provides NEGATIVE feedback Easiest explanation: A collector emitter bias circuit provides negative feedback as well as requires multiples resistors for a small change. The negative feedback limits the frequency range it will work in. Higher frequencies will provide poor performance. It also requires a GREATER number of resistors just to provide a stability against a small parameter.

Discussion

21.	What is the magnitude of voltage generated at emitter circuit of a CE short circuit current frequency response model?(a) hre × hfe / Ib × RL(b) hre × hfe × Ib × RL(c) hre × hfe / IC × RL(d) hre × hfe × IC × RLThe question was posed to me in an internship interview.My question is from The CE Short Circuit Current Frequency Response in section High Frequency Transistor of Electronic Devices & Circuits
Answer» Right choice is (b) hre × hfe × Ib × RL The explanation: The magnitude of voltage generated at emitter CIRCUIT of a common emitter (CE) amplifier can be expressed in terms of hybrid parameters in the CE short circuit CURRENT frequency response model. The magnitude of voltage generated is equal to hre × hfe × Ib × RL where, RL is LOAD resistance and Ib is the BASE current.

Discussion

22.	Where does degeneration take place in a self – alpha cutoff frequency?(a) Across RB(b) Across RE(c) No degeneration occurs(d) Across RCI got this question in final exam.I would like to ask this question from The Alpha Cutoff Frequency topic in division High Frequency Transistor of Electronic Devices & Circuits
Answer» CORRECT answer is (b) Across RE Explanation: Degeneration or negative feedback occurs across RE which in turn stabilizes the fluctuations of current IE due to TEMPERATURE changes and variations in VBE and α. In a stable alpha cutoff frequency, the variations in the VALUE of VBE and α do not affect the stability of the system.

Discussion

23.	How does emitter resistor RE provide stability in CE short circuit gain obtained with hybrid pi model?(a) Consumes less power(b) Has an easier circuit design(c) Automatically biases the circuit(d) It does not provide stabilityThis question was posed to me in an online interview.The question is from The CE Short Circuit Gain Obtained with the Hybrid PI Model in section High Frequency Transistor of Electronic Devices & Circuits
Answer» The correct answer is (c) AUTOMATICALLY biases the circuit To elaborate: In a CE short circuit gain obtained with hybrid pi model, the EMITTER resistor provides stability by automatically BIASING the circuit using negative FEEDBACK. The negative feedback negates any CHANGE due to the collector current with an opposing change provided by the base bias voltage and thus helps maintain circuit stability.

Discussion

24.	What are the hybrid-pi conductance in low frequency H-parameters used to analyze?(a) MOSFET(b) Junction Field Effect Transistor(c) Bipolar Junction Transistor(d) It has no useThis question was addressed to me by my college professor while I was bunking the class.Query is from Hybrid PI Conductances in Low Frequency H Parameters topic in division High Frequency Transistor of Electronic Devices & Circuits
Answer» The correct option is (C) Bipolar Junction Transistor The best EXPLANATION: The four hybrid-pi conductance in LOW frequency H-parameters of a two-port network are used to analyze the workings of a Bipolar Junction Transistor or in other words a BJT. The inverse hybrid-pi conductance in low frequency H-parameters are used to analyze the Junction Field Effect Transistor of JFET.

Discussion

25.	How is the current gain of a current gain with resistive load amplifier?(a) Irrelevant(b) Moderate(c) Low(d) HighThe question was posed to me in semester exam.I'm obligated to ask this question of Current Gain with Resistive Load topic in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» The correct CHOICE is (d) High The best I can explain: The construction of a current GAIN with resistive load circuit are approximately SIMILAR to a REGULAR feedback amplifier. Nonetheless, one of the most striking differentiating FEATURE of a current gain with resistive load circuit is its high current gain.

Discussion

26.	What is the function of a capacitor in the linear analysis of a transistor?(a) To find the operating point(b) To block d-c signals(c) To block a-c signals(d) Makes no differenceI had been asked this question in class test.My question is taken from Transistor Amplifier Response, Taking Source Resistance into Account in section High Frequency Transistor of Electronic Devices & Circuits
Answer» RIGHT option is (b) To block d-c signals The best EXPLANATION: Capacitors are used in the linear analysis of a transistor circuit TAKING source resistance into account to block out and ISOLATE the d-c signals while letting the a-c signals pass through. This is USEFUL to calculate the load line in the analysis of the transistor.

Discussion

27.	In an ideal stable self – alpha cutoff frequency, what should be the current IBwith respect to IC?(a) IB should be 20% of IC(b) IB should be 5% of IC(c) IB should be 10% of IC(d) IB should be 50% of ICThe question was posed to me by my college professor while I was bunking the class.The above asked question is from The Alpha Cutoff Frequency in chapter High Frequency Transistor of Electronic Devices & Circuits
Answer» Correct option is (c) IB should be 10% of IC Easy explanation: IDEALLY, the RESISTOR values are designed in a way that the VOLTAGE drop across RE is approximately 10% of Vcc and IB should be 10% of Ic. Hence, stable self – alpha cutoff frequency work best at low power supply VOLTAGES.

Discussion

28.	Collector base feedback and emitter feedback combined together provide stability for self – alpha cutoff frequency.(a) True(b) FalseI have been asked this question in an online interview.I want to ask this question from The Alpha Cutoff Frequency in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» Correct option is (a) True To explain I would say: COLLECTOR base FEEDBACK and emitter feedback combined provide stability for self – alpha CUTOFF frequency. This is because the emitter base JUNCTION is forward biased due to the voltage drop across RE.

Discussion

29.	How do you calculate the value of VCE in CE short circuit gain obtained with hybrid pi model?(a) VCE = VCC + IC (RC + RE)(b) VCE = VCC – IC (RC + RE)(c) VCE = VCC – IC (RB + RE)(d) VCE = VCC + IC (RB + RE)I got this question in homework.This question is from The CE Short Circuit Gain Obtained with the Hybrid PI Model in section High Frequency Transistor of Electronic Devices & Circuits
Answer» The correct OPTION is (b) VCE = VCC – IC (RC + RE) Explanation: The value of VCE can be calculated USING this equation: VCE = VCC – IC (RC + RE). It is the voltage between the collector and emitter terminal of the transistor and is measured as the OUTPUT of the transistor.

Discussion

30.	What is the value of voltage gain in the hybrid-pi CE transistor model?(a) hfe × RL / hre(b) –hfe × RL / hre(c) hfe × RL / hie(d) –hfe × RL / hieThe question was asked during an online exam.My enquiry is from The Hybrid PI CE Transistor Model topic in chapter High Frequency Transistor of Electronic Devices & Circuits
Answer» Correct option is (d) –HFE × RL / hie Explanation: The voltage gain of a common emitter (CE) AMPLIFIER can be expressed in terms of hybrid parameters in the hybrid-pi CE TRANSISTOR MODEL. The voltage gain is equal to -hfe × RL / hie where, RL is load resistance, hie is input resistance and -hfe is the current gain.

Discussion

31.	We can measure hybrid h-parameters using inverse hybrid g-parameters.(a) True(b) FalseThe question was posed to me in quiz.I want to ask this question from Hybrid PI Conductances in Low Frequency H Parameters topic in chapter High Frequency Transistor of Electronic Devices & Circuits
Answer» The correct CHOICE is (a) True The explanation: The hybrid h-PARAMETERS can be MEASURED USING the inverse hybrid g-parameters. All the parameters used to analyze a two-port NETWORK can be used to convert and measure other different parameters.

Discussion

32.	How do we calculate the value of IC in the hybrid-pi CE transistor model?(a) IC = hre × IB(b) IC = -hre × IB(c) IC = hfe × IB(d) IC = -hfe × IBThis question was addressed to me during an online exam.This interesting question is from The Hybrid PI CE Transistor Model topic in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» The correct answer is (c) IC = hfe × IB Explanation: The COLLECTOR current of a COMMON emitter (CE) AMPLIFIER can be expressed in terms of hybrid parameters in the hybrid-pi CE transistor model. It is expressed as the product of hfe × IB . This is the same for APPROXIMATE hybrid models as well.

Discussion

33.	What is the value of output resistance in the CE short circuit current frequency response model?(a) ∞(b) 0(c) hic(d) hieThis question was posed to me during an internship interview.This interesting question is from The CE Short Circuit Current Frequency Response topic in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» The correct answer is (a) ∞ Easiest explanation: The output resistance in a simplified common emitter hybrid model is calculated as the ratio of COLLECTOR voltage over collector current while VS is equal to zero and RL is omitted. Due to this CONFIGURATION IC is equal to zero and hence output resistance is infinite.

Discussion

34.	We use hybrid-pi CE transistor model to obtain approximate values.(a) True(b) FalseI got this question in my homework.My query is from The Hybrid PI CE Transistor Model in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» Correct answer is (a) True To explain I WOULD say: It is more practical to calculate the approximate values of VOLTAGE and current gains instead of COMPUTING the EXACT values of a common emitter amplifier circuit. We use a simplified common emitter hybrid model to obtain these approximate values without reducing the accuracy.

Discussion

35.	What is the value of input resistance in the CE short circuit current frequency response model?(a) hoe(b) hib(c) hic(d) hieThe question was posed to me at a job interview.This is a very interesting question from The CE Short Circuit Current Frequency Response in division High Frequency Transistor of Electronic Devices & Circuits
Answer» Right option is (d) hie Explanation: The input resistance of a COMMON emitter (CE) amplifier can be expressed in terms of HYBRID parameters in the CE short circuit current FREQUENCY response model. The input resistance is universally expressed as hie. This is also the same for APPROXIMATE as well as exact hybrid models.

Discussion

36.	Where is the output measured in a CB short circuit current frequency response?(a) Collector terminal(b) Emitter terminal(c) Base terminal(d) GroundThe question was asked at a job interview.My query is from The CB Short Circuit Current Frequency Response in division High Frequency Transistor of Electronic Devices & Circuits
Answer» Correct ANSWER is (a) Collector terminal Easy EXPLANATION: In the physical model of a CB short circuit current frequency RESPONSE the output is measured at the collector terminal of the BJT biased device. WHEREAS, the input is measured ACROSS the emitter terminal of the biased BJT device.

Discussion

37.	What is the function of RE in the CE short circuit gain obtained with hybrid pi model?(a) To improve stability and decrease positive feedback(b) To improve stability and increase positive feedback(c) To improve stability and decrease negative feedback(d) To improve stability and increase negative feedbackThis question was addressed to me in a job interview.I would like to ask this question from The CE Short Circuit Gain Obtained with the Hybrid PI Model in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» Correct OPTION is (d) To improve stability and INCREASE negative feedback The BEST I can explain: In a CE short circuit gain obtained with hybrid pi model circuit, the emitter resistor provides additional stability along with increasing the negative feedback sent to the collector. The addition of the emitter resistance enables the transistor’s emitter to no longer be GROUNDED to zero – volt potential.

Discussion

38.	Which parameter of the physical model is varied while measuring the input characteristics of a CB short circuit current frequency response?(a) Emitter current(b) Emitter voltage(c) Collector current(d) Emitter base voltageThe question was asked at a job interview.The doubt is from The CB Short Circuit Current Frequency Response in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» Right OPTION is (d) EMITTER base VOLTAGE Easiest explanation: To determine the INPUT characteristics, the collector – base voltage is kept constant at zero volts and the emitter base voltage is INCREASED from zero volts to different voltage levels. For each voltage level of the input voltage, the input current is recorded.

Discussion

39.	In a high frequency T model, which parameter is known as the output conductance?(a) h11(b) h12(c) h21(d) h22The question was asked in semester exam.This interesting question is from The High Frequency T Model in section High Frequency Transistor of Electronic Devices & Circuits
Answer» Correct answer is (d) h22 To explain: When the input TERMINAL of a two-port device is open circuited in a HIGH frequency T MODEL, the input current flowing equals to zero. Hence the value of h22 = I2 / V2. The unit of this PARAMETER is ampere / volt or mho. Hence it is KNOWN as output conductance.

Discussion

40.	What is the T represent in high frequency T model?(a) Transmission(b) Transistor(c) Tailgate(d) ThoroughThe question was asked in an internship interview.This intriguing question comes from The High Frequency T Model in chapter High Frequency Transistor of Electronic Devices & Circuits
Answer» CORRECT answer is (b) Transistor The best I can explain: The T in high frequency T model REPRESENTS transistor MODELS. This demonstrates the study of high frequency input operations on multiple BASIC transistor models to observe the VARIATION in the output characteristics.

Discussion

41.	Which of the following is an independent variable in a linear analysis of a common base transistor?(a) Collector emitter voltage(b) Collector current(c) Emitter base voltage(d) Emitter currentI had been asked this question in an interview for internship.I want to ask this question from Transistor Amplifier Response, Taking Source Resistance into Account in chapter High Frequency Transistor of Electronic Devices & Circuits
Answer» The correct choice is (d) Emitter CURRENT To EXPLAIN I would SAY: In a linear analysis of a common base transistor, we have two independent variables. The emitter current is an independent variable and the emitter base voltage is the dependent variable. We can obtain VEB USING IE from the characteristic CURVE.

Discussion

42.	What is the value power gain in the CE short circuit current frequency response model?(a) AV – AI(b) AV + AI(c) AV × AI(d) AV / AII got this question during an interview.This question is from The CE Short Circuit Current Frequency Response topic in division High Frequency Transistor of Electronic Devices & Circuits
Answer» Right answer is (C) AV × AI Easiest explanation: The power gain in a simplified COMMON emitter hybrid model is CALCULATED as the product of voltage gain and power gain. It is EXPRESSED as AV × AI. It can also be further simplified as AI^2 × RL / Ri, where RL is load resistance and Ri is input resistance.

Discussion

43.	Why do we need CE short circuit gain obtained with hybrid pi model?(a) To provide a non – linear output(b) To maintain transistor in active region(c) To maintain transistor in saturation region(d) To maintain transistor in cut – off regionI got this question in a national level competition.The doubt is from The CE Short Circuit Gain Obtained with the Hybrid PI Model in division High Frequency Transistor of Electronic Devices & Circuits
Answer» Right choice is (b) To maintain transistor in ACTIVE REGION For explanation I WOULD say: We use a CE short circuit gain obtained with hybrid pi model to collect negative feedback and to maintain the transistor in an active region. To maintain stability in active region, the DC base biased voltage is RESULTANT from the collector voltage VC .

Discussion

44.	What is the stability factor if RE = 8kΩ and RTH = 11kΩ during alpha cutoff frequency?(a) 1.335(b) 2.375(c) 1.727(d) 0.272The question was asked by my college professor while I was bunking the class.This question is from The Alpha Cutoff Frequency in chapter High Frequency Transistor of Electronic Devices & Circuits
Answer» Right option is (B) 2.375 Explanation: STABILITY factor is CALCULATED by the following equation. On plugging in the given VALUES RE = 8kΩ and RTH = 11kΩ, we get: S = 1 + RTH / RE S = 1 + 11 / 8 = 2.375.

Discussion

45.	What is the value of overall voltage gain in the hybrid-pi CE transistor model while considering RS ?(a) VB / VS(b) VC / VS(c) VB × VS(d) VC × VSI have been asked this question by my college professor while I was bunking the class.Query is from The Hybrid PI CE Transistor Model topic in section High Frequency Transistor of Electronic Devices & Circuits
Answer» CORRECT choice is (a) VB / VS To elaborate: The overall VOLTAGE gain in a simplified common EMITTER hybrid model while considering RS is CALCULATED as RATIO of base voltage over the applied external voltage. It is expressed as VB / VS . Where, VS is the external applied voltage on the amplifier.

Discussion

46.	What is the value of output resistance in the hybrid-pi CE transistor model?(a) ∞(b) 0(c) hic(d) hieI had been asked this question during an interview.My doubt is from The Hybrid PI CE Transistor Model in section High Frequency Transistor of Electronic Devices & Circuits
Answer» Right choice is (a) ∞ The best I can EXPLAIN: The output resistance in a simplified common EMITTER hybrid model is calculated as the RATIO of collector voltage over collector current while VS is EQUAL to zero and RL is omitted. Due to this CONFIGURATION IC is equal to zero and hence output resistance is infinite.

Discussion

47.	What is the path of the input characteristic of a CB short circuit current frequency response?(a) Linear(b) Exponential decrease(c) Exponential increase(d) ConstantThe question was asked in my homework.The above asked question is from The CB Short Circuit Current Frequency Response topic in section High Frequency Transistor of Electronic Devices & Circuits
Answer» Right choice is (a) Linear Best explanation: In a CB short circuit CURRENT frequency response, the INPUT CHARACTERISTIC curve increases EXPONENTIALLY. The emitter current increases exponentially with respect to emitter base voltage for fixed VALUES of collector base voltage.

Discussion

48.	Which parameter of the physical model is varied while measuring the output characteristics of a CB short circuit current frequency response?(a) Emitter current(b) Emitter voltage(c) Collector current(d) Collector base voltageI had been asked this question in exam.The query is from The CB Short Circuit Current Frequency Response in section High Frequency Transistor of Electronic Devices & Circuits
Answer» Correct answer is (d) Collector base voltage Explanation: To determine the OUTPUT characteristics, the emitter current is kept constant at zero and the collector base voltage is increased from zero VOLTS to VARYING voltage levels. For each voltage level of the output voltage, the collector current is RECORDED.

Discussion

49.	Which hybrid parameter is used to calculate forward current gain in a high frequency T model?(a) h11(b) h12(c) h21(d) h22I got this question at a job interview.Query is from The High Frequency T Model topic in section High Frequency Transistor of Electronic Devices & Circuits
Answer» Right choice is (C) h21 To elaborate: The hybrid parameter h21 can be calculated by short CIRCUITING the output port in a high FREQUENCY T model. By doing so, we can calculate h21 = I2 / I1. Since this is a ratio between two current units, h21 is unit LESS. It is known as the FORWARD current gain of the circuit.

Discussion

50.	What is the equation of the load line in the linear analysis of a transistor?(a) VCE = VCC + IB RL(b) VCE = VCC – IB RL(c) VCE = VCC + IC RL(d) VCE = VCC – IC RLThe question was asked in an interview for job.Enquiry is from Transistor Amplifier Response, Taking Source Resistance into Account topic in portion High Frequency Transistor of Electronic Devices & Circuits
Answer» Correct answer is (d) VCE = VCC – IC RL The best explanation: Let the collector voltage supply be VCC in series with a load resistor RL. A straight line superimposed on the collector characteristic will PROVIDE US with the load line. The EQUATION for the load line is VCE = VCC – IC RL.

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