List of top Electronics and Communication Engineering Questions

Consider the circuit with an ideal OPAMP shown in the figure. 
Assuming \( |V_{IN}| \ll |V_{CC}| \) and \( |V_{REF}| \ll |V_{CC}| \), the condition at which \( V_{OUT} \) equals to zero is

For the circuit with an ideal OPAMP shown in the figure, \( V_{REF} \) is fixed. 

If \( V_{OUT} = 1 \, \text{volt} \) for \( V_{IN} = 0.1 \, \text{volt} \) and \( V_{OUT} = 6 \, \text{volt} \) for \( V_{IN} = 1 \, \text{volt} \), where \( V_{OUT} \) is measured across \( R_L \) connected at the output of this OPAMP, the value of \( \frac{R_F}{R_{IN}} \) is:

The energy band diagram of a p-type semiconductor bar of length \( L \) under equilibrium condition (i.e., the Fermi energy level \( E_F \) is constant) is shown in the figure. The valance band \( E_V \) is sloped since doping is non-uniform along the bar. The difference between the energy levels of the valence band at the two edges of the bar is \( \Delta \). 

If the charge of an electron is \( q \), then the magnitude of the electric field developed inside this semiconductor bar is 
 

A standard air-filled rectangular waveguide with dimensions \( a = 8 \, \text{cm}, b = 4 \, \text{cm} \), operates at 3.4 GHz. For the dominant mode of wave propagation, the phase velocity of the signal is \( v_p \). The value (rounded off to two decimal places) of \( v_p / c \), where \( c \) denotes the velocity of light, is
For a vector field \( \mathbf{D} = \rho \cos^2 \phi a_{\rho} + z^2 \sin^2 \phi a_{\phi} \) in a cylindrical coordinate system \( (\rho, \phi, z) \) with unit vectors \( a_{\rho}, a_{\phi}, a_z \), the net flux of \( \mathbf{D} \) leaving the closed surface of the cylinder \( (\rho = 3, 0 \leq z \leq 2) \) (rounded off to two decimal places) is .
Consider the vector field \( \mathbf{F} = a_x (4y - c_1 z) + a_y (4x + 2z) + a_z (2y + z) \) in a rectangular coordinate system \( (x, y, z) \) with unit vectors \( a_x, a_y, a_z \). If the field \( \mathbf{F} \) is irrotational (conservative), then the constant \( c_1 \) (in integer) is _________.
A bar of silicon is doped with boron concentration of \( 10^{16} \, \text{cm}^{-3} \) and assumed to be fully ionized. It is exposed to light such that electron-hole pairs are generated throughout the volume of the bar at the rate of \( 10^{20} \, \text{cm}^{-3} \, \text{s}^{-1} \). If the recombination lifetime is 100 µs, intrinsic carrier concentration of silicon is \( 10^{10} \, \text{cm}^{-3} \) and assuming 100\% ionization of boron, then the approximate product of steady-state electron and hole concentrations due to this light exposure is