GATE EC || ELECTRONIC DEVICES AND CIRCUIT|| BJT || PYQS(2000-2025)

Last Updated :
Discuss
Comments

Question 1

The impurity commonly used for realizing the base region of a silicon n-p-n transistor is  


(GATE 2014 || EC || MCQ||1 MARK)

  • Gallium

  •  Indium

  •  Boron

  • Phosphorus

Question 2

The neutral base width of a bipolar transistor, biased in the active region, is 0.5 μm. The maximum electron concentration and the diffusion constant in the base are 1014/cm3 and Dn = 25 cm2/sec respectively in the base, the collector current density is (the electron charge is 1.6 × 10–19 Coulomb)

(GATE 2004 || EC || MCQ|| 1 MARK)

  • 800 A/cm2

  • 8 A/cm2

  • 200 A/cm2

  • 2 A/cm2

Question 3

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 0.2V, then the transistor is operating in the

(GATE 2004 || EC || MCQ||1 MARK)

  • normal active mode

  •  saturation mode

  • inverse active mode

  • cutoff mode

Question 4

Consider the following statements S1 and S2. 

S1: The β of a bipolar transistor reduces if the base width is increased.

S2: The β of a bipolar transistor increases if the doping concentration in the base is increased. 

Which one of the following is correct? 


(GATE 2004 || EC || MCQ||1 MARK)

  •  S1 is FALSE and S2 is TRUE

  • Both S1 and S2 are TRUE

  •  Both S1 and S2 are FALSE

  • S1 and TRUE and S2 is FALSE

Question 5

The phenomenon known as “Early Effect” in a bipolar transistor refers to a reduction of the effective base-width caused by

(GATE 2006 || EC || MCQ||1 MARK)

  •  electron-hole recombination at the base 

  •  the reverse biasing of the base-collector junction

  • the forward biasing of emitter-base junction

  • the early removal of stored base charge during saturation to-cut-off switching

Question 6

For a BJT, the common-base current gain α = 0.98 and the collector base junction reverse bias saturation current IC0 = 0.6 μA. This BJT is connected in the common emitter mode and operated in the active region with a base drive current IB = 20 μA. The collector current Ic for this mode of operation is 

(GATE 2011 || EC || NAT || 1 MARK)

  • 0.98 mA

  • 0.99 mA

  • 1.0 mA

  • 1.01 mA

Question 7

A BJT is biased in forward active mode. Assume VBE = 0.7 V, kT/q = 25 mV and reverse saturation current Is = 10–13 mA. The transconductance of the BJT (in mA/V) is.


(GATE 2014 || EC || MCQ||1 MARK)

  • (5.7 to 5.9)

Question 8

Consider two BJTs biased at the same collector current with area, A1 = 0.2 μm×0.2 μm and A2 = 300 μm×300 μm. Assuming that all other device parameters are identical kT/q = 26 mV, the intrinsic carrier concentrations is 1 × 1010 cm–3, and q = 1.6 × 10–19 C, the difference between the base-emitter voltages (in mV) of the two BJTs (i.e., VBE1- VBE2) is __

(GATE 2014 || EC || NAT||1 MARK)

  • 381

Question 9

If the base width in a bipolar junction transistor is doubled, which one of the following statements will be TRUE? 


(GATE 2014 || EC || MCQ||1 MARK)

  •  Current gain will increase

  •  Unity gain frequency will increase

  •  Emitter base junction capacitance will increase.

  •  Early voltage will increase

Question 10

In a uniformly doped BJT, assume that NE, NB and NC are the emitter, base and collector doping in atoms/cm3, respectively. If the emitter injection efficiency of the BJT is close to unity, which one of the following conditions is TRUE?


(GATE 2010 || EC || MCQ||1 MARK)

  • NE = NB = NC

  •  NE>> NB and NB> NC

  • NE = NB and NB< NC

  • NE< NB< NC

There are 14 questions to complete.

Take a part in the ongoing discussion