371. For the circuit shown in the figure the voltage gain is | VO/ VS | = AV Given gm =	1	β = 100, AV is given by—
     	25

     
     
     

1. 1. 100

   
   
   

   2. 800

   
   
   

   3. 80 x	10
      	11

   
   
   

   4. 40

   
   
   

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1. View Hint View Answer Discuss in Forum

   Given RC = 2 k, AVS = | | V0 VS, gm =	1	, β = 100, AV =?
   	25

   
   
   we know that
   g_m r _π= β
   

   rπ =		β	=	100	= 2500
   		gm		1/25

   
   

   Vπ= VS.	2.5 k
   	(2.5 k + 2.5 k)

   
   By applying potential divider rule and neglecting 25k being very high.
   Now, V_o = g_m V_π. R_C
   

   or Vo =		1	× VS.		2.5		· 2000
   		25			5

   
   

   or		Vo	=	2000
   		VS		50

   
   

   or Ar =	Vo	= 40
   	VS

   
   Hence alternative (D) is the correct answer.

   Correct Option: D

   Given RC = 2 k, AVS = | | V0 VS, gm =	1	, β = 100, AV =?
   	25

   
   
   we know that
   g_m r _π= β
   

   rπ =		β	=	100	= 2500
   		gm		1/25

   
   

   Vπ= VS.	2.5 k
   	(2.5 k + 2.5 k)

   
   By applying potential divider rule and neglecting 25k being very high.
   Now, V_o = g_m V_π. R_C
   

   or Vo =		1	× VS.		2.5		· 2000
   		25			5

   
   

   or		Vo	=	2000
   		VS		50

   
   

   or Ar =	Vo	= 40
   	VS

   
   Hence alternative (D) is the correct answer.

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372. I_C the d_c collector current of a BJT = 2 mA at room temperature where kT/q = 25 m volts. Given h_fe = 100, the value of h_ie is given by—

1. 1. 125 ohm

   
   
   

   2. 25 ohm

   
   
   

   3. 1250 ohm

   
   
   

   4. 2500 ohm

   
   
   

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1. View Hint View Answer Discuss in Forum

   Given, IC = 2 mA,	kT	= 25 mV, hge = 100,
   	q

   
   we know that
   β = g_m r_π (where β = h_fe = 100)
   

   =		Ic	=	2 × 10–3
   		kT / q		25 × 10–3

   
   

   So, rπ = hie =		β	=	100	= 1250
   		gm		2 / 25

   
   Hence alternative (C) is the correct answer.

   Correct Option: C

   Given, IC = 2 mA,	kT	= 25 mV, hge = 100,
   	q

   
   we know that
   β = g_m r_π (where β = h_fe = 100)
   

   =		Ic	=	2 × 10–3
   		kT / q		25 × 10–3

   
   

   So, rπ = hie =		β	=	100	= 1250
   		gm		2 / 25

   
   Hence alternative (C) is the correct answer.

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373. 
     

     RS = 3 k. Given	V0	= 0.9, the value of gm is given by—
     	VS

1. 1. 0.3 mA/V

   
   
   

   2. 0.33 mA/V

   
   
   

   3. 3.0 mA/V

   
   
   

   4. 3.0 A/V

   
   
   

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1. View Hint View Answer Discuss in Forum

   Given that AVS =	V0	= 0.9, RS = 3 k, gm =?
   	VS

   
   

   AV =	RS
   	RS +( 1 / gm)

   
   

   0.9 =	3kΩ
   	RS +( 1 / gm)

   
   or g_m = 3 mA/V
   Hence alternative (C) is the correct answer.

   Correct Option: C

   Given that AVS =	V0	= 0.9, RS = 3 k, gm =?
   	VS

   
   

   AV =	RS
   	RS +( 1 / gm)

   
   

   0.9 =	3kΩ
   	RS +( 1 / gm)

   
   or g_m = 3 mA/V
   Hence alternative (C) is the correct answer.

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374. 
     Given g_m = 3 × 10^{– 3}. R_S = 3000. R_O is given by—

1. 1. 3000

   
   
   

   2. 	1000
      	3

   
   
   

   3. 300

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   Given that g_m = 3 × 10^{– 3}
   R_S = 3 k
   R₀ =?
   R₀ is the common drain configuration is given as,
   

   R0 = RS ||	1
   	gm

   
   

   or R0 = 3000 ||	1
   	3 × 10–3

   
   

   or R0 =	3000 × (1000 / 3)
   	3000 + (1000 / 3)

   
   or R₀ = 300 Ω
   Hence alternative (C) is the correct answer.

   Correct Option: C

   Given that g_m = 3 × 10^{– 3}
   R_S = 3 k
   R₀ =?
   R₀ is the common drain configuration is given as,
   

   R0 = RS ||	1
   	gm

   
   

   or R0 = 3000 ||	1
   	3 × 10–3

   
   

   or R0 =	3000 × (1000 / 3)
   	3000 + (1000 / 3)

   
   or R₀ = 300 Ω
   Hence alternative (C) is the correct answer.

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375. A Field-Effect Transistor (FET)—

1. 1. Uses a high-concentration emitter junction

   
   
   

   2. Uses a forward-biased PN-junction

   
   
   

   3. Has a very high input resistance

   
   
   

   4. Depends on minority-carrier flow

   
   
   

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1. View Hint View Answer Discuss in Forum

   A field-effect transistor (FET) is very high input resistance that’s why FET is a better switch than BJT (Bipolar junction transistor).

   Correct Option: C

   A field-effect transistor (FET) is very high input resistance that’s why FET is a better switch than BJT (Bipolar junction transistor).

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