GATE EC Electronic Devices questions

Consider avalanche breakdown in a silicon $p^{+}n$ junction. The $n$-region is uniformly doped with a donor density $N_{D}.$ Assume that breakdown occurs when the magnitude of the electric field at any point in the device becomes equal to the critical field $E_{crit}.$ Assume $E_{crit}$ to be independent of $N_{D}$. If the built-in voltage of the …

Consider a region of silicon devoid of electrons and holes, with an ionized donor density of $N_{d}^{+}=10^{17} cm^{-3}.$ The electric field at $x = 0$ is $0\: V/cm$ and the electric field at $x=L$ is $50$ $kV/cm$ in the positive $x$ direction, Assume that the electric field is zero in the $y$ and $z$ directions at all points. Given …

The figure shows a half-wave rectifier with a $475 \: \mu F$ filter capacitor. The load draws a constant current $I_{o}= 1 \: A$ from the rectifier. The figure also shows the input voltage $V_{i}$, the output voltage $V_{C}$ and the peak-to-peak voltage ripple $u$ on $V_{C}$. The input voltage $V_{i}$ is a triangle-wave with an amplitude of …

In the opamp circuit shown, the Zener diodes $Z1$ and $Z2$ clamp the output voltage $V_{0}$ to $+5V$ or $-5 V$. The switch $S$ is initially closed and is opened at time $t=0$. The time $t=t_{1}$ (in seconds) at which $V_{0}$ changes state is ________

The parallel-plate capacitor shown in the figure has movable plates. The capacitor is charged so that the energy stored in it is $E$ when the plate separation is $d$. The capacitor is then isolated electrically and the plate are moved such that the plate separation becomes $2d$. At this new plate separation, what is the energy stored in the capacitor, …

The figure shows the band diagram of a Metal Oxide Semiconductor (MOS). The surface region of this MOS is in

The figure shows the $I-V$ characteristics of a solar cell illuminated uniformly with solar light of power $100\ mW/cm^2$. The solar cell has an area of $3\ cm^2$ and a fill factor of $0.7$. The maximum efficiency (in $\%$) of the device is _______

In the figure shown, the current $i$ (in ampere) is _________

Figures I and II show two MOS capacitors of unit area. The capacitor in Figure I has insulator materials $X$ (of thickness $t_1 = 1$ nm and dielectric constant $\varepsilon_1=4$) and $Y$ (of thickness $t_2 = 3$ nm and dielectric constant $\varepsilon_2 = 20$). The capacitor in Figure II has only insulator material $X$ of thickness $t_{Eq}$. …

The $I-V$ characteristics of the zener diodes $D1\:\text{and}\:D2$ are shown in Figure I. These diodes are used in the circuit given in Figure II. If the supply voltage is varied from $0$ to $100$ V,then breakdown occurs in

For the circuit shown in the figure, $R_1=R_2=R_3=1\;\Omega,\;L=1\:\mu H$ and $C=1\:\mu F$. If the input $V_{in}=\cos(10^6t)$, then the overall voltage gain $(V_{out}/V_{in})$ of the circuit is _________

In the given circuit, the values of $V_1$ and $V_2$ respectively are

A region of negative differential resistance is observed in the current voltage characteristics of a silicon PN junction if

A silicon sample is uniformly doped with donor type impurities with a concentration of $10^{16} / cm^3$. The electron and hole mobilities in the sample are $1200 \: cm^2/V-s$ and $400 \: cm^2/V-s$ respectively. Assume complete ionization of impurities. The charge of an electron is $1.6 \times 10^{-19} \:C$. The resistivity of the sample (in …

In the circuit shown below, the Zener diode is ideal and the Zener voltage is $6$ V. The output voltage $V_o$ (in volts) is ________.

In the circuit shown, the switch SW is thrown from position $A$ to position $B$ at time $t=0$. The energy (in $\mu J$) taken from the $3$ V source to charge the $0.1 \: \mu F$ capacitor from $0$ V t $3$ V is

Consider a straight, infinitely long, current carrying conductor lying on the z-axis. Which one of the following plots (in linear scale) qualitatively represents the dependence of $H_{\phi}$ on $r$, where $H_{\phi}$ is the magnitude of the azimuthal component of magnetic field outside the conductor and $r$ is the radial distance from the conductor?

The built-in potential of an abrupt p-n junction is $0.75$ V. If its junction capacitance $(C_J)$ at a reverse bias $(V_R)$ of $1.25 \: V$ is $5$ pF, the value of $C_J$ (in pF) when $V_R = 7.25 \: V$ is ________.

For a silicon diode with long P and N regions, the accepter and donor impurity concentrations are $1 \times 10^{17} \:cm^{-3}$ and $1 \times 10^{15} \: cm^{-3}$, respectively. The lifetimes of electrons in P region and holes in N region are both $100 \: \mu s$. The electron and hole diffusion coefficients are $49 \: cm^2/s$ and $36 \: cm^2/s$, …

An $n$-type silicon sample is uniformly illuminated with light which generates $10^{20}$ electron-hole pairs per $cm^{3}$ per second. The minority carrier lifetime in the sample is $1\mu s$. In the steady state, the hole concentration in the sample is approximately $10^{x}$, where $x$ is an integer. The value of $x$ is _______.