The total thermal resistance of a power transistor and heat sink is 20°C/W. The ambient temperature is 25°C and (TJ)MAX=200°C. If VCE=4V, find the maximum collector current that the transistor can carry without destruction. What will be the allowed value of collector current if ambient temperature rises to 75°C?

The total thermal resistance of a power transistor and heat sink is 20°C/W. The ambient temperature is 25°C and (TJ)MAX=200°C. If VCE=4V, find the maximum collector current that the transistor can carry without destruction.

A

3.67A

B

7.56A

C

2.19A

D

4.16A

A silicon power transistor is operated with a heat sink HS-A=1.5°C/W. The transistor rated at 150W (25°C) has HJ-C=0.5°C/W and the mounting insulation has HC-S=0.6°C/W. What maximum power can be dissipated if the ambient temperature is 40°C and (TJ)MAX=200°C?

A

70.6W

B

61.5W

C

37.8W

D

56.9W

Difference between the active heat sink and passive heat sink is that passive heat sink?

A

Possess mechanical components

B

Possess electrical components

C

Do not possess mechanical components

D

Do not possess metal components

Consider an NMOS transistor having kn= 2 mA/V2. Let the transistor be biased at VOV = 1V. For operation in saturation, what dc bias current ID results? If a +0.1-V signal is superimposed on VGS, find the corresponding increment in collector current by evaluating the total collector current ID and subtracting the dc bias current ID.

A

ID = 1mA and Increment = 0.21 mA

B

ID = 1mA and Increment = 0.42 mA

C

ID = 2mA and Increment = 0.21 mA

D

ID = 2mA and Increment = 0.42 mA

Given collector resistance = 2kΩ, load resistance = 5kΩ, collector capacitance = 1μF, emitter capacitance = 20μF, collector current = 2mA, source resistance = 2kΩ. If the effect of blocking capacitor is ignored, find the applicable cut-off frequency.

A

22.73 Hz

B

612 Hz

C

673Hz

D

317 Hz

For a given transistor, the thermal resistance is 8°C/W and for the ambient temperature TA is 27°C. If the transistor dissipates 3W of power, calculate the junction temperature (TJ).

A

51°C

B

27°C

C

67°C

D

77°C

Determine the value of emitter current and collector current of a transistor having α=0.98 and collector to base leakage current ICBO=4µA. The base current is 50µA.

A

1.5mA

B

3.7mA

C

2.7mA

D

4.5mA

A thermal reservoir at 538°C is brought into thermal communication with another thermal reservoir at 260°C, and as a result 1055 kJ of heat is transferred only from the higher to lower temperature reservoir. Determine the change in entropy of the universe due to the exchange of heat between these two thermal reservoirs.

A

0.378182 kJ/K

B

0.478182 kJ/K

C

0.578182 kJ/K

D

0.678182 kJ/K

Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow and k = Thermal conductivity of the body)

A

$${\text{kA}}\frac{{{\text{dT}}}}{{{\text{dx}}}}$$

B

$${\text{kA}}\frac{{{\text{dx}}}}{{{\text{dT}}}}$$

C

$${\text{k}}\frac{{{\text{dT}}}}{{{\text{dx}}}}$$

D

$${\text{k}}\frac{{{\text{dx}}}}{{{\text{dT}}}}$$

A germanium transistor used as an amplifier has a collector cut off current ICBO=10µA at a temperature 27°C and β=50. What is the collector current when the base current is 0.25mA?

A

10.76mA

B

13.01mA

C

15.67mA

D

11.88Ma