Physics

Suppose a n-type wafer is'created by doping Si crystal having 5 x 10²⁸atoms/m³ with 1 ppm concentration of As. On the surface 200 ppm boron is added to create 'p' region in this wafer. Considering n_i = 1.5 x 10¹⁶ m^-3,
(i) Calculate the densities of the charge carriers in the n and p regions,
(ii) Comment which charge carriers would contribute largely for the reverse saturation current when diode is reverse biased.

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This is a Long Answer Type Questions as classified in NCERT Exemplar

whem As is used then it will create n type semiconductor

N_e=N_D= $\frac{1}{10^{6}} * 5 * 10^{28} = 5 * 10^{22} / m^{3}$

Number of minority carriers n_h= $\frac{{n i}^{2}}{n e} = \frac{{(1.5 * 10^{16})}^{2}}{5 * 10^{22}}$ = 0.45 $* 10^{10} / m^{3}$

But when B is implanted in Si crystal then p type semiconductor is formed

N_h=N_A= $\frac{200}{10^{6}} * (5 * 10^{28}) = 1 * 10^{25} / m^{3}$

Minority carriers created in p type is

N_e= $\frac{{n i}^{2}}{n e} = \frac{({1.5 * 10^{16})}^{2}}{1 * 10^{25}} = 2.25 * 10^{27} / m^{3}$

Minority charge carriers holes in p type would contribute more in reverse saturatiom current.

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7 months ago

Suppose a n-type wafer is‘created by doping Si crystal having 5 x 10²⁸atoms/m³ with 1 ppm concentration of As. On the surface 200 ppm boron is added to create ‘p’ region in this wafer. Considering n_i = 1.5 x 10¹⁶ m^-3,
(i) Calculate the densities of the charge carriers in the n and p regions,
(ii) Comment which charge carriers would contribute largely for the reverse saturation current when diode is reverse biased.

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7 months ago

Consider the circuit arrangement shown in Fig 14.16 (a) for studying input and output characteristics of npn transistor in CE configuration

Select the values of RB and RC for a transistor whose VBE = 0.7 V, so that the transistor is operating at point Q as shown in the characteristics shown in Fig. 14.16 (b). Given that the input impedance of the transistor is very small and VCC = VBB = 16 V, also find the voltage gain and power gain of circuit making appropriate assumptions.

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This is a Long Answer Type Questions as classified in NCERT Exemplar

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7 months ago

Assuming the ideal diode, draw the output waveform for the circuit given in figure, explain the waveform.

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This is a Long Answer Type Questions as classified in NCERT Exemplar

Explanation- When the input voltage is equal to or less than 5 V, diode will be revers biased. It will offer high resistance in comparison to resistance ( ) R in series. Now, diode appears in open circuit. The input waveform is then passed to the output terminals. The result with sin wave input is to dip off all positive going portion above 5 V.

If input voltage is more than + 5 V, diode will be conducting as if forward biased offering low resistance in comparison to R. But there will be no voltage in output beyond 5 V as the

voltagebeyond+5Vwillappearacross R.

When

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7 months ago

Draw the output signals C₁ and C₂ in the given combination of gates.

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A B	C D	E F	G	H	I	C₁
0 0	0 0	1 1	1	0	0	1
1 0	1 0	0 1	0	1	1	0
0 1	0 1	1 0	0	1	1	0
1 1	1 1	0 0	0	1	1	0

A B	C D	E F	G	C2
0 0	0 0	1 1	1	0
1 0	1 0	0 1	1	0
0 1	0 1	1 0	1	0
1 1	1 1	0 0	0	1

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7 months ago

In the circuit shown in figure, when the input voltage of the base resistance is 10 V, V_BEis zero and V_CE is also zero. Find the values of I_B, I_C and β .

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This is a Long Answer Type Questions as classified in NCERT Exemplar

Explanation- voltage across R_B= 10V

Resistance R_B= 400kohm

V_BE= 0, V_CE= 0, R_c=3kohm

I_B= voltage /R_B= 10/400 $*$ 10³= 25 $*$ 10^-6A

Voltage across R_c= 10V

I_c=voltage/R_c= 10/3 $*$ 10³= 3.33 $*$ 10^-3

$β = \frac{I_{c}}{I_{B}} = \frac{3.33 * 10^{- 3}}{25 * 10^{- 6}} = 133$

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7 months ago

If each diode in figure has a forward bias resistance of 25 Ω and infinite resistance in reverse bias, what will be the values of the currents I₁, I₂, I₃and I₄?

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Contributor-Level 10

This is a Long Answer Type Questions as classified in NCERT Exemplar

forward biased resistance = 25ohm

Reverse biased resistance = infinity

As CD branch is reverse biased having infinite resistance.

So I₃= 0

Resistance in branch AB= 25+125= 150 ohm (R₁)

Resistance in branch EF= 25+125= 150 ohm (R₂)

They both are in parallel

So $\frac{1}{R} = \frac{1}{R_{1}} + \frac{1}{R_{2}} = \frac{1}{150} + \frac{1}{150} = \frac{2}{150}$

R= 75ohm

So total resistance = 25+75= 100ohm

Current = V/R= 5/100=0.05A

I₁=I₂+I₃+I₄

I₁=I₄+I₂

Here the resistance R₁ and R₂ is same

I₄=I₂

I₁= 2I₂

I₂= I₁/2=0.05/2=0.025A

I₄= 0.025A

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7 months ago

Which of the following would produce analog signals and which would produce digital signals?
(a) A vibrating tuning fork
(b) Musical sound due to a vibrating sitar string
(c) Light pulse
(d) Output of NAND gate

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This is a Multiple Choice Questions as classified in NCERT Exemplar

Analog and digital signals are used to transmit information, usually through electric signals. In both these technologies, the information such as any audio or video is

transformed into electric signals.

The difference between analog and digital technologies is that in analog technology, information is translated into electric pulses of varying amplitude. In digital technology, translation of information is into binary formal (zero or one) where each bit is representative of two distinct amplitudes.

Thus, (a) and (b) would produce analog signal and (c) and (d) would produc

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7 months ago

In amplitude modulation, the modulation index m is kept less than or equal to 1 because
(a) m> 1, will result in interference between carrier frequency and message frequency, resulting into distortion.
(b) m > 1, will result in overlapping of both side bands resulting into loss of information
(c) m > 1, will result in change in phase between carrier signal and message signal.
(d) m > 1, indicates amplitude of message signal greater than amplitude of carrier signal resulting into distortion.

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This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer- b, d

Explanation- modulation index m= A_m/A_c

If m>1 then A_m>A_c

maximum modulation frequency m_f= frequency deviation / maximum frequency of modulating wave

here if m>1 then it means overlapping of both sides resulting loss of information.

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7 months ago

The frequency response curve (figure) for the filter circuit used for production of AM wave should be

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