36. The hybrid-π parameter values of g_m, r_π and r₀ are:

1. 1. 24 mA/V, ∞, 5 kΩ

   
   
   

   2. 24 mA/V, 5 kΩ, ∞

   
   
   

   3. 48 mA/V, 10 kΩ, 18.4 kΩ

   
   
   

   4. 48 mA/V, 18.4 kΩ, 10 kΩ

   
   
   

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1. View Hint View Answer Discuss in Forum

   Given that, β = 120
   V_A = ∞
   

   IB =	2 – VBE	=	2 – 7	= 5.2 µA
   	250 kΩ		250 kΩ

   
   I_CQ = β I_B = 120 × 5.2 × 10^–6 = 0.642 mA
   Now,

   gm =	ICQ	=	·642 × 10–3	= 24 mA/V
   	VT		26 × 10–3

   
   

   rπ =	β	=	120	= 5 kΩ
   	gm		24 × 10–3

   
   

   r0 =	| VA |	=	∞	= ∞
   	ICQ		24 × 10–3

   Correct Option: B

   Given that, β = 120
   V_A = ∞
   

   IB =	2 – VBE	=	2 – 7	= 5.2 µA
   	250 kΩ		250 kΩ

   
   I_CQ = β I_B = 120 × 5.2 × 10^–6 = 0.642 mA
   Now,

   gm =	ICQ	=	·642 × 10–3	= 24 mA/V
   	VT		26 × 10–3

   
   

   rπ =	β	=	120	= 5 kΩ
   	gm		24 × 10–3

   
   

   r0 =	| VA |	=	∞	= ∞
   	ICQ		24 × 10–3

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37. If the transistor parameter are β = 180 and early voltage V_A = 140 V and it is biased at I_CQ = 2 mA, the values of hybrid-π parameter g_m, r_x and r₀ are respectively:

1. 1. 14 A/V, 2.33 kΩ, 90 kΩ

   
   
   

   2. 14 A/V, 90 kΩ, 2.33 kΩ

   
   
   

   3. 77 mA/V, 2.33 kΩ, 70 kΩ

   
   
   

   4. 77.2 A/V, 70 kΩ, 2.33 kΩ

   
   
   

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1. View Hint View Answer Discuss in Forum

   gm =	IC Q	=	2 × 10–3	= 0.0769 ≈ 77 mA/V
   	VT		26 × 10–3

   
   

   rπ =	β	=	180	= 2.33 kΩ
   	gm		77 × 10–3

   
   

   r0 =	| VA |	=	140	= 70 kΩ
   	ICQ		2 × 10–3

   Correct Option: C

   gm =	IC Q	=	2 × 10–3	= 0.0769 ≈ 77 mA/V
   	VT		26 × 10–3

   
   

   rπ =	β	=	180	= 2.33 kΩ
   	gm		77 × 10–3

   
   

   r0 =	| VA |	=	140	= 70 kΩ
   	ICQ		2 × 10–3

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38. The bandwidth of an RF tuned amplier is dependent on:

1. 1. Q-factor of the tuned output circuit

   
   
   

   2. Q-factor of the tuned input circuit

   
   
   

   3. Quiescent operating point

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   Bandwidth =	f0
   	Q

   
   where, f₀ = resonant frequency & Q = quality factor

   Correct Option: A

   Bandwidth =	f0
   	Q

   
   where, f₀ = resonant frequency & Q = quality factor

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39. Match each of the items A, B and C with and appropriate item from 1, 2, 3, 4 and 5.
    (A) Common-collector amplifier.
    (B) Common-emitter amplifier.
    (C) Common-base amplifier.
    1. provides voltage gain but no current gain
    2. provides current gain but no voltage gain
    3. provides neither voltage nor power gain
    4. provides neither current nor power gain
    5. provides both voltage and current gain

1. 1. A-5, B-3, C-1

   
   
   

   2. A-2, B-5, C-2

   
   
   

   3. A-4, B-1, C-2

   
   
   

   4. A-2, B-5, C-1

   
   
   

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1. View Hint View Answer Discuss in Forum

   A – 2
   B – 5
   C – 1

   Correct Option: D

   A – 2
   B – 5
   C – 1

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40. Match each of the items A, B and C with and appropriate item from 1, 2, 3, 4 and 5. In an extrinsic semiconductor:
    (A) the resistivity decreases
    (B) the temperature coefficient of resistivity is negative.
    (C) the photo conductivity is low
    1. the doping concentration is low
    2. the length of the semiconductor is reduced
    3. the band gap is high
    4. the area of cross-section of the semiconductor is increased
    5. the doping concentration is increased

1. 1. A-3, B-3, C-1

   
   
   

   2. A-5, B-5, C-3

   
   
   

   3. A-2, B-4, C-5

   
   
   

   4. A-4, B-1, C-2

   
   
   

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1. View Hint View Answer Discuss in Forum

   A – 5
   B – 5
   C – 1

   Correct Option: B

   A – 5
   B – 5
   C – 1

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