Semiconductors — JEE Main PYQs

A message single of frequency 20 kHz and peak voltage of 20 volt is used to modulate a carrier wave of frequency 1 MHz and peak voltage of 20 volt. The modulation index will be _____.

In a semiconductor, the number density of intrinsic charge carriers at $27^{\circ }\mathrm{C}$ is $1.5\times 10^{16}/{\mathrm{m}}^3$. If the semiconductor is doped with impurity atom, the hole density increases to $4.5\times 10^{22}/{\mathrm{m}}^3$. The electron density in the d …

Find the truth table for the function $Y$ of $A$ and $B$ represented in the following figure.

The maximum amplitude wave is found to be 12 V while the minimum amplitude is found to be 3 V . The modulation index is 0.6 x where x is ____ .

A carrier wave with amplitude of 250 V is amplitude modulated by a sinusoidal base band signal of amplitude 150 V. The ratio of minimum amplitude to maximum amplitude for the amplitude modulated wave is 50 : $x$, then value of $x$ is ______.

In the logic circuit shown in the figure, if input A and B are 0 to 1 respectively, then output at Y would be ' x '.
The value of $x$ is ____

The following logic gate is equivalent to:

The correct relation between $\alpha$ ( ratio of collector current to emitter current ) and $\beta$ ( ratio of collector current to base current) of a transistor is :

The typical output characteristics curve for a transistor working in the common-emitter configuration is shown in the figure.

The estimated current gain from the figure is ____

Which one of the following will be the output of the given circuit?

A carrier signal $\mathrm{C}(\mathrm{t})=25\sin \left(2.512\times 10^{10}\mathrm{t}\right)$ is amplitude modulated by a message signal $\mathrm{m}(\mathrm{t})=5\sin \left(1.57\times 10^8\mathrm{t}\right)$ and transmitted through an antenna. What will be the bandwidth of t …

Match List - I with List - II.

List - I
(a) 10 km height over earth's surface
(b) 70 km height over earth's surface
(c) 180 km height over earth's surface
(d) 270 km height over earth's surface

List - II
(i) Thermosphere
(ii) Mesosphere
(iii) Stratosphere
(iv) Troposphere

An npn transistor operates as a common emitter amplifier with a power gain of $10^6$. The input circuit resistance is $100\Omega$ and the output load resistance is $10\mathrm{k}\Omega$. The common emitter current gain ' $\beta$ ' will be ⋯------. (Round off to the Ne …

Which of the following given a reversible operation?

Boolean relation at the output state-Y for the following circuits is:

In the given circuit, value of Y is

Both the diodes used in the circuit shown are assumed to be ideal and have negligible resistance when these are forward biased. Built in potential in each diode is 0.7 V. For the input voltages shown in the figure, the voltage (in Volts) at point $A$ is ____.

Two Zener diodes (A and B) having breakdown voltages of 6 V and 4 V respe4ctively, are connected as shown in the circuit below. The output voltage ${\mathrm{V}}_0$ variation wlith input voltage linearly increasing with time, is given by: ( ${\mathrm{V}}_{\text{input }}=0$ V at …

Which of the following will NOT be observed when a multimeter (operating in resistance measuring mode) probes connected across a component, are just reversed?

The out put characteristics of a transistor is shown in the figure. When ${\mathrm{V}}_{\mathrm{CE}}$ is 10 V and ${\mathrm{I}}_{\mathrm{C}}=4.0$ mA, then value of ${\beta }_{\mathrm{ac}}$ is ____.

Take the breakdown voltage of the zener diode used in the given circuit as 6 V . For the input voltage shown in figure below, the time variation of the output voltage is:
(Graphs drawn are schematic and not to scale)

Identify the operation performed by the circuit given below:

The reverse breakdown voltage of a Zener diode is 5.6 V in the given circuit .

The current ${\mathrm{I}}_{\mathrm{z}}$ through the Zener is:

A common emitter amplifier circuit, built using an npn transistor, is shown in the figure. Its dc current gain is $250,R_C=1k\Omega$ and $V_{CC}=10V$. What is the minimum base current for $V_{CE}$ to reach saturation?

An NPN transistor is used in common emitter configuration as an amplifier with $1\mathrm{k}\Omega$ load resistance. Signal voltage of 10 mV is applied across the base-emitter. This produces a 3 mA change in the collector current and $15\mu \mathrm{A}$ change in the base c …

A signal $A\cos \omega t$ is transmitted using $v_0\sin {\omega }_{0}t$ as carrier wave. The correct amplitude modulated (AM) signal is:

To get output ' 1 ' at R , for the given logic gate circuit the input values must be:

An amplitude modulated signal is plotted below:

Which one of the following best described the above signal?

The transfer characteristic curve of a transistor, having input and output resistance 100 $\Omega$ and $100\mathrm{k}\Omega$ respectively, is shown in the figure. The Voltage and Power gain, are respectively :

The truth table for the circuit given in the fig is :

In the given circuit the current through Zener Diode is close to:

A 100 V carrier wave is made to vary between 160 V and 40 V by a modulating signal. What is the modulation index?

The output of the given logic circuit is:

Figure shown a DC voltage regulator circuit, with a Zener diode of breakdown voltage = 6 V . If the unregulated input voltage varies between 10 V to 16 V , then what is the maximum Zener current?

In an amplitude modulator circuit, the carrier wave is given by, $\mathrm{C}(\mathrm{t})=4\sin (20000\pi \mathrm{t})$ while modulating signal is given by, $\mathrm{m}(\mathrm{t})=2\sin (2000\pi \mathrm{t})$. The values of modulation index and lower side band frequency are:

In the figure, given that $V_{BB}$ supply can vary from 0 to 5.0 V, $V_{cc}=5V$, ${\beta }_{dc}=200$, $R_B=100k\Omega$, $R_C=1k\Omega$ and $V_{BE}=1.0V$. The minimum base current and the input voltage at which the transistor will go to saturation, will be respectively:

To double the covering range of a TV transition tower, its height should be multiplied by :

The logic gate equivalent to the given logic circuit is:

The physical sizes of the transmitter and receiver antenna in a communication system are:

Ge and Si diodes start conducting at 0.3 V and 0.7 V respectively. In the following figure if Ge diode connection are reversed, the value of ${\mathrm{V}}_0$ changes by: (assume that the Ge diode has large breakdown voltage)

An npn transistor operates as a common emitter amplifier, with a power gain of 60 dB . The input circuit resistance is $100\Omega$ and the output load resistance is $10\mathrm{k}\Omega$. the common emitter current gain $\beta$ is:

A message signal of frequency 100 MHz and peak voltage 100 V is used to execute amplitude modulation on a carrier wave of frequency 300 GHz and peak voltage 400 V. The modulation index and difference between the two side band frequencies are:

The reading of the ammeter for a silicon diode in the given circuit is :

A telephonic communication service is working at carrier frequency of 10 GHz. Only $10\%$ of it is utilized for transmission. How many telephonic channels can be transmitted simultaneously if each channel requires a bandwidth of 5 kHz?

In amplitude modulation, sinusoidal carrier frequency used is denoted by ${\omega }_{\mathrm{c}}$ and the signal frequency is denoted by ${\omega }_{\mathrm{m}}$. The bandwidth ( $\Delta {\omega }_{\mathrm{m}}$ ) of the signal is such that …

In a common emitter amplifier circuit using an $\mathrm{n}-\mathrm{p}-\mathrm{n}$ transistor, the phase difference between the input and the output voltages will be :

Choose the correct statement :

Identify the semiconductor devices whose characteristics are given below, in the order (a), (b), (c), (d) :

If $\mathrm{a},\mathrm{b},\mathrm{c},\mathrm{d}$ are inputs to a gate and x is its output, then, as per the following time graph, the gate is:

For a common emitter configuration, if $\alpha$ and $\beta$ have their usual meanings, the incorrect relationship between $\alpha$ and $\beta$ is: