NTA UGC NET/JRF Exam, February-2023 (Electronic Science)

Total Questions: 100

1. In case a reverse biased photodiode is kept in dark condition, the current flowing through the device corresponds to:

Correct Answer: A. Maximum value of current which can flow through the device
Solution:

A photodiode operates by absorbing photons and converting them to a current across the device. When it is reverse-biased and kept in the dark, it doesn't receive any photons. Hence, there is no photo-generated current. However, due to thermal energy, a tiny amount of current called the reverse saturation current (or dark current) flows.

This is the minimum current flowing through the device when no photons are absorbed. It's essential to keep in mind that the reverse saturation current is a very small value, and it is the baseline current for a reverse-biased photodiode in the dark.

2. The diode used in fig. below has the threshold voltage of 0.5 V and a forward resistance of 42. Calculate the current flow Iᴅ through and the voltage drop Vᴅ across the diode.

Correct Answer: C. Iᴅ = 4.482 mA, Vᴅ = 0.52 V

3. What current should flow through D₂ diode? Consider the values given in circuit below.

Correct Answer: C. 3.11 mA

4. The ratio of peak-to-peak input ripple voltage to peak-to-peak ripple output voltage is known as:

Correct Answer: D. Ripple rejection
Solution:

Ripple rejection refers to the ability of a circuit, often a power supply oror amplifier, to suppress or reduce the amount of ripple voltage from its input to its output. A higher ripple rejection ratio indicates a better suppression of input ripple. In mathematical terms, ripple rejection is given as:
This essentially measures the effectiveness of a circuit in filtering out unwanted fluctuations (ripple) from a desired signal.

5. Answer the question below :

Correct Answer: C.
Solution:

The oxide capacitance for a MOS transistor is dependent on its mode of operation. In the saturation mode, the drainto-gate overlap results in an effective
This capacitance can influence the dynamic behavior of the MOSFET, especially at high frequencies, and is an essential parameter in RF circuit design and analysis.

6. In a MOS transistor, if n⁺ region is diffused in p-type substrate, the type of pn junction generated towards channel and drain is:

Correct Answer: B. n⁺/p
Solution:

When an n⁺ region is diffused into a p-type substrate in a MOS transistor, the junction created between the channel and the drain is between the n⁺ region and the р substrate. Therefore, the type of junction formed is n⁺/p.

7. Answer the question below :

Correct Answer: B. 42 x 10⁻⁵ A/V²
Solution:

For an n-channel MOS transistor, the value of the K parameter, also known as the transconductance parameter, is given by:

8. Consider a resistive load inverter with

Correct Answer: D. 5 V
Solution:

9. For series RLC circuit given below in figure, choose the correct answer based on Kirchoff s voltage law from following:

Correct Answer: B.

10. Unit parabolic function is represented by its Laplace transform as:

Correct Answer: B. 1/s³