GATE ECE on Transistor's Practice Test

1. A Bipolar Transistor is Operating in the active region with a collector current of 1mA. Assuming that the β of the transistor is 100 and the thermal Voltage (V_t) is 25mV,the trans conductance(g_m) and the input resistance (r_π) of the transistor in the common emitter Configuration, are

A. g_m = 25mA/V & r_π =15.625KOhm

B. g_m = 40mA/V & r_π = 4.0KOhm

C. g_m = 25mA/V & r_π = 2.5KOhm

D. g_m = 40mA/V & r_π = 2.5KOhm

2. In the Following transistor Circuit,V_BE=0.7V and r_e= 25mV/IE ,and β large all the capacitance's are very Large .The Value of DC Current I_E is

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A.1mA

B.2mA

C.5mA

D.10mA

The mid -band voltage gain of the amplifier is approximately

A. -180

B. -120

C. -90

D. -60

3.The Transistor amplifier shown in figure is biased with a current source I and has a very large β the value of C is very large .V_BE =0.7V ,T=300 K

1.The DC Collector Voltage is

A. 1V

B. 2V

C.3V

D. 4V

2. The low Frequency small signal Voltage Gain Av=vo/v_i is

A. 40

B. 80

C. 120

D. 160

4. A Small signal source V_i(t) = A cos 20t+ B sin 10^6t is applied to a transistor amplifiers as shown below. The transistor has β =150 and h_ie=3kohm .Which expression best approximates v_o (t)?

A. Vo ( t) = -1500 (A cos 20t + B sin 10^6 t )

B. Vo ( t) = -150 (A cos 20t + B sin 10^6 t )

C. Vo ( t) = -1500 B sin 10^6 t

D. Vo ( t) = -150 B sin 10^6 t

5. In the Transistor amplifier circuit shown in the figure below ,the transistor has the Following . parameters

β_Dc=60,V_be =0.7V,h_ie à infinity,h_fe à infinity.The capacitance CC can be assumed to be infinite. In the figure above ,the ground has been shown by the symbol

1.Under the DC conditions ,the collector -to- emitter Voltage drop is

A. 4.8 Volts

B. 5.3 Volts

C. 6.0 Volts

D. 6.6 Volts

2. If BDC is increased by 10% ,the collector -to-emitter Voltage drop

A. Increases by less than or equal to 10%

B. Decreases by less than or equal to 10%

C. Increases by More than 10%

D. Decreases by More than 10%

3. The small signal gain of the amplifier Vc/Vs is

A. -10

B. -5.3

C. 5.3

D. 10

6.In the Circuit shown below , capacitors C1 and C2 are very large and are short at the input frequency . Vi is a small signal input.The gain magnitude |vo/vi| at 10 Mrad/s is

A. Maximum

B. Minimum

C. Unity

D. Zero

7.The current i_b through the base of a silicon npn transistor is 1+0.1cos (10000πt)mA.At 300 K, the r_π in the small signal model of the transistor is