Electronic Devices — JEE Main PYQs

If $X$ and $Y$ are the inputs, the given circuit works as ________.

[Figure: Logic circuit — input X passes through a NAND gate (both inputs tied to X), input Y passes through a NAND gate (both inputs tied to Y); the two outputs feed a NAND gate whose output goes through another NAND gate (both inputs tied together) to the Output.]

Two 4 bits binary numbers, $A = 1101$ and $B = 1010$ are given in the inputs of a logic circuit shown in figure below. The output ($Y$) will be :

[Figure: Logic circuit — input $A$ passes through a NOT gate; its output and input $B$ feed a NAND gate whose output is $Y$]

Consider a circuit consisting of a capacitor (20 μF), resistor (100 Ω) and two identical diodes as shown in figure. The resistance of diode under forward biasing condition is 10 Ω. The time constant of the circuit is $\alpha \times 10^{-3}$ s. The value of $\alpha$ is _________.

[Figure: Circuit with battery $V$, capacitor $C = 20\ \mu\text{F}$ in the top branch, resistor $R = 100\ \Omega$ in series with two identical diodes connected in parallel with opposite polarities]

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R

Assertion A: A diode under reverse-biased condition provides very small current which is nearly independent of voltage until a critical limit at which the current increases drastically.

Reason R: Below the critical voltage limit, only majority charge carriers flow which increases drastically above critical voltage.

Choose the correct answer from the options given below

A diode has Zener voltage of $10 \text{ V}$ and maximum power dissipation of $0.5 \text{ W}$, then the minimum resistance to be used in series with this diode for safety when it is connected to a $25 \text{ V}$ power supply is ________ $\Omega$.

For the given logic circuit, which of the following inputs combination will make both LED$-$1 and LED$-$2 to glow?

[Figure: Logic circuit with inputs A, B, C. Inputs A and B feed an OR gate whose output drives LED-1 (through a resistor to ground) and also feeds one input of an AND gate; input C feeds the other input of the AND gate. The AND gate output and a line from A feed a final gate whose output drives LED-2 through a resistor.]

In a semiconductor p-n diode, the doping concentrations on p-side and n-side are $10^{15} \text{ atoms/cm}^3$ and $10^{18} \text{ atoms/cm}^3$, respectively. Which one of the following statements is true ?

The maximum rated power of the LED is 2 mW and it is used in the circuit with input voltage of 5 V as shown in the figure below. The current through resistance $R_S$ is 0.5 mA.

The minimum value of the resistance of $R_S$, to ensure that the LED is not damaged is ________ $\text{k}\Omega$.

[Figure: A 5 V source in series with resistance $R_S$; the circuit then splits into two parallel branches: one with $R = 1\ \text{k}\Omega$ in series with a diode, and the other with a 2 mW LED]

Refer to the logic circuit given below. For two inputs $(A = 1,\ B = 1)$ and $(A = 0,\ B = 1)$, output $(Y)$ will be __________.

[Figure: Logic circuit — input A passes through a NOT gate; the NOT-gate output and B feed an OR gate; A (via the inverter branch) and B also feed an AND gate; the OR-gate and AND-gate outputs feed a NOR gate whose output is Y.]

The output $Y$ for the given inputs $A$ and $B$ to the circuit is :

[Figure: input waveforms — $A$ is 1 from $t = 1$ to $t = 3$ (0 elsewhere), $B$ is 1 from $t = 0$ to $t = 1$ and after $t = 2$; circuit — $A$ and $B$ feed two AND gates (each gate taking one direct and one shared input) whose outputs feed an OR gate giving $Y$]

A zener diode with 5 V zener voltage is used to regulate an unregulated dc voltage input of 25 V. For a $400~\Omega$ resistor connected in series, the zener current is found to be 4 times load current. The load current $(\mathrm{I_L})$ and load resistance $(\mathrm{R_L})$ are :

In the digital circuit shown in the figure, for the given inputs the P and Q values are :

[Figure: logic circuit with both inputs equal to 1; a NAND gate feeds one input of a gate giving output P, and the inputs also pass through NOT gates into an OR/NOR combination whose output (through further gates) gives Q]

Choose the correct logic circuit for the given truth table having inputs A and B.

Inputs		Output
A	B	Y
0	0	0
0	1	0
1	0	1
1	1	1

The truth table corresponding to the circuit given below is :

[Figure: logic circuit — inputs A and B feed an OR gate; the OR gate output and input A feed an AND gate whose output is C]

Consider a n-type semiconductor in which $\mathrm{n_e}$ and $\mathrm{n_h}$ are number of electrons and holes, respectively.

(A) Holes are minority carriers (B) The dopant is a pentavalent atom (C) $\mathrm{n_e n_h} \neq \mathrm{n}_i^2$ (where $\mathrm{n}_i$ is number of electrons or holes in semiconductor when it is intrinsic form) (D) $\mathrm{n_e n_h} \geqslant \mathrm{n}_i^2$ (E) The holes are not generated due to the donors

Choose the correct answer from the options given below :

In the following circuit, the reading of the ammeter will be

(Take Zener breakdown voltage = 4 V)

[Figure: a 12 V battery in series with a 100 Ω resistor; across the output, a Zener diode, a voltmeter (V) and a 400 Ω resistor in parallel, with an ammeter (A) in the 400 Ω branch]

Consider the following logic circuit.

[Figure: logic circuit — inputs A and B feed an AND gate; a branch of the inputs, one passed through a NOT gate, feeds an OR gate; the AND and OR outputs feed a NAND gate whose output is Y]

The output is $Y = 0$ when :

The output voltage in the following circuit is (Consider ideal diode case)

[Figure: circuit with two diodes — D$_1$ with its anode side connected to a +5V input and D$_2$ with its anode side connected to ground; the cathodes of both diodes join at a common node which connects through a resistor to +5V supply and to the output terminal V$_{out}$]

Which of the following circuits represents a forward biased diode ?

[Figure: five circuits — (A) diode with p-side terminal at −10 V and n-side terminal at 0 V; (B) diode with p-side at −10 V and n-side at −15 V; (C) diode with p-side at 4 V and n-side at 2 V; (D) diode with n-side terminal at −5 V and p-side terminal at −10 V; (E) diode with n-side connected to ground and p-side terminal at 2 V]

Choose the correct answer from the options given below :

[Figure: logic circuit — inputs A and B are fed directly to one AND gate; A and B are also fed through NOT gates to a second AND gate; the outputs of both AND gates are fed to a gate G whose output is Y]

A	B	Y
0	0	1
0	1	0
1	0	0
1	1	1

To obtain the given truth table, the following logic gate should be placed at G :

Refer to the circuit diagram given in the figure. which of the following observations are correct?

A. Total resistance of circuit is 6 $\Omega$

B. Current in Ammeter is 1A

C. Potential across AB is 4 Volts.

D. Potential across CD is 4 Volts

E. Total resistance of the circuit is 8 $\Omega$.

Choose the correct answer from the options given below:

[Figure: circuit with battery E = 6 V in series with an ammeter leading to node C; a 4 $\Omega$ resistor from C down to node D; from D one branch has a 4 $\Omega$ resistor to the bottom rail and a second branch passes through a forward-biased diode to node A, then a 4 $\Omega$ resistor from A down to node B on the bottom rail]

What is the current through the battery in the circuit shown below ?

[Figure: circuit with two parallel branches, each containing a diode in series with a $20~\Omega$ resistor; both diodes are oriented in the same direction; the parallel combination is connected across a 5 V battery]

Consider the following statements:

A. The junction area of solar cell is made very narrow compared to a photo diode.

B. Solar cells are not connected with any external bias.

C. LED is made of lightly doped p-n junction.

D. Increase of forward current results in continuous increase of LED light intensity.

E. LEDs have to be connected in forward bias for emission of light.

Choose the correct answer from the options given below:

The output of the circuit is low (zero) for :

[Figure: logic circuit — inputs X and Y feed an OR gate; the OR gate's output passes through a NOT (inverting) gate to give the final output]

(A) $X = 0,\ Y = 0$

(B) $X = 0,\ Y = 1$

(C) $X = 1,\ Y = 0$

(D) $X = 1,\ Y = 1$

Choose the correct answer from the options given below :

Which of the following circuits has the same outpur as that of the given circuit?

[Figure: logic circuit — inputs A and B; B is passed through a NOT gate; one AND gate receives A and NOT B, another AND gate receives A and B; the outputs of the two AND gates feed a NOR gate whose output is Y]

[Figure: an AC source $V = V_0\sin\omega t$ connected in a circuit; a resistor R is in parallel between terminals A (top) and B (bottom), and a diode is in the lower branch of the loop]

In the circuit shown here, assuming threshold voltage of diode is negligibly small, then voltage $V_{AB}$ is correctly represented by :

The value of net resistance of the network as shown in the given figure is :

[Figure: three parallel branches between terminals at $-6$ V and $-8$ V — top branch: 15 Ω resistor; middle branch: 10 Ω resistor in series with a diode pointing toward the $-8$ V terminal; bottom branch: 5 Ω resistor in series with a diode pointing toward the $-6$ V terminal]

Identify the logic gate given in the circuit:

[Figure: inputs A and B each pass through a NOT gate (inverter); the two inverted outputs feed a two-input OR-shaped gate whose output carries a bubble (inversion), giving output Y]

Following gates section is connected in a complete suitable circuit.

[Figure: logic circuit — input A through a NOT/NOR gate, inputs B and C through a NAND gate, both outputs feeding a NOR gate; input D through an OR gate; the NOR gate output and the OR gate output connect through a resistance R to a DC bulb]

For which of the following combination, bulb will glow (ON) :

The output (Y) of logic circuit given below is 0 only when :

[Figure: logic circuit — inputs A and B feed an OR gate; input B and a constant input 1 feed an AND gate; the outputs of the OR gate and the AND gate feed a final OR gate whose output is Y]

The correct truth table for the following logic circuit is :

[Figure: logic circuit — inputs A and B feed an AND gate; input A also passes through a NOT gate; the NOT-gate output and the AND-gate output feed an OR gate whose output is Y]

The acceptor level of a p-type semiconductor is 6 eV. The maximum wavelength of light which can create a hole would be : Given $hc = 1242\ \mathrm{eV\,nm}$.

The output Y of following circuit for given inputs is :

[Figure: logic circuit — inputs A and B; A and NOT(B) feed an OR gate; B and NOT(A) feed an AND gate; outputs of the OR and AND gates feed a final AND gate giving Y]

A potential divider circuit is connected with a dc source of 20 V, a light emitting diode of glow in voltage 1.8 V and a zener diode of breakdown voltage of 3.2 V. The length (PR) of the resistive wire is 20 cm. The minimum length of PQ to just glow the LED is __________ cm.

[Figure: a 20 V dc source across a resistive wire PR with sliding contact Q; an LED is connected from P and a zener diode from the LED junction back to the tap at Q]

A light emitting diode (LED) is fabricated using GaAs semiconducting material whose band gap is 1.42 eV. The wavelength of light emitted from the LED is :

[Figure: logic circuit — inputs A and B feed an AND gate whose output goes to one input of a NOR gate giving output E; A and B also each pass through NOT gates into a second AND gate whose output goes to the other input of the NOR gate]

Truth table:

A	B	E
0	0	0
0	1	X
1	0	Y
1	1	0

In the truth table of the above circuit the value of X and Y are :

The $I$-$V$ characteristics of an electronic device shown in the figure. The device is :

[Figure: I–V curve — small current for positive V rising near the origin, and for negative V a nearly constant small reverse current of $5(\mu A)$ that drops sharply at a large negative (breakdown) voltage]

In the given circuit if the power rating of Zener diode is 10 mW, the value of series resistance $R_s$ to regulate the input unregulated supply is :

[Figure: an unregulated supply $V_s = 8\,\mathrm{V}$ in series with resistor $R_s$, feeding a Zener diode ($V_z = 5\,\mathrm{V}$) in parallel with a load resistor $R_L = 1\,\mathrm{k\Omega}$]

Conductivity of a photodiode starts changing only if the wavelength of incident light is less than 660 nm. The band gap of photodiode is found to be $\left(\frac{X}{8}\right)$ eV. The value of X is :

(Given, $h = 6.6 \times 10^{-34}$ Js, $e = 1.6 \times 10^{-19}$ C)

Which of the following circuits is reverse - biased ?

In the given circuit, the breakdown voltage of the Zener diode is 3.0 V. What is the value of $\mathrm{I_z}$?

[Figure: circuit with a 10 V battery in series with a 1 kΩ resistor; a Zener diode (carrying current $I_z$) connected between nodes A and B in parallel with a 2 kΩ resistor connected between nodes C and D across the output terminals]

A Zener diode of breakdown voltage 10 V is used as a voltage regulator as shown in the figure. The current through the Zener diode is :

[Figure: 20 V battery in series with a $200~\Omega$ resistor; a Zener diode in parallel with a branch containing a $500~\Omega$ resistor]

[Figure: series circuit with a 15 V battery, diode $D_1$ (Ge) and diode $D_2$ (Si) both forward biased, a $1.5\ k\Omega$ resistor, and a load resistance $R_L = 2.5\ k\Omega$ across which the voltage is measured]

In the given circuit, the voltage across load resistance $(R_L)$ is:

Identify the logic operation performed by the given circuit.

[Figure: logic circuit — inputs A and B each pass through a NOT gate (inverter), whose outputs feed a NAND gate giving output Y]

[Figure: logic circuit — inputs A and B; A and NOT(B) feed an OR gate; B and NOT(A) feed a second OR gate; the two OR outputs feed a NOR gate whose output is Y]

The output of the given circuit diagram is -