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The depletion capacitance, C_j of an abrupt p-n junction with constant doping on either side varies with reverse bias, V_R, as:
(C_j)α(V_R)^-1/2
An inductance of 0.08 μH is large than _______.
0.000000008 H
A certain JFET has a g_m = 4 mS with an external ac drain resistance of 1.5 kΩ. What is the ideal voltage gain?
6
What is the probability that an electron in a metal occupies the Fermi-level, at any temperature (>0 K)?
0.5
In unbiased p-n junction, thickness of depletion layer is of the order of:
0.5 μm
What is the ratio of the output impedance with series feedback to that without feedback?
1 + βA
Consider the following statements: pure germanium and pure silicon are examples of: 1. Direct band-gap semiconductors 2. Indirect band-gap semiconductors 3. Degenerate semiconductors Of these statements:
1 alone is correct
Consider the following statements: Compared to Silicon, Gallium Arsenide (GaAs) has: 1. Higher signal speed since electron mobility is higher 2. Poorer crystal quality since stoichiometric growth difficult 3. Easier to grow crystals since the vapor pressure Arsenic is high 4. Higher optoelectronic conversion efficiency Of these statements:
3 and 4 are correct
There is 900 mA of current through a wire with 40 turns. What is the reluctance of the circuit if the flux is 400 Wb?
90000 At/Wb
Silicon is not suitable for fabrication of light emitting diodes because it is:
A direct band gap semiconductor
Hall effect is observed in a specimen when it (metal or a semiconductor) is carrying current and is placed in a magnetic field. The resultant electric field inside the specimen will be in:
A direction normal to both current and magnetic field
What is the circuit number of the IC that contains four two-input AND gates in standard TTL?
7408
The clipping action of a diode requires that its forward resistance:
Be zero
If the temperature of an extrinsic semiconductor is increased so that the intrinsic carrier concentration is doubled, then:
Both majority and minority carrier densities double
The disadvantages of capacitor input LC filter are:
High cost, more weight and external field produced by a series inductor
Which of the following most probably exists when a slow blinking robe light happens to a logic probe placed on the input of a digital circuit?
High frequency pulse train
At room temperature, the current in an intrinsic semiconductor is due to:
Holes and electrons
For a C-C configuration to operate properly, the collector-base junction should be reverse biased, while forward bias should be applied to which junction?
Collector-emitter
Which of the following configurations has a voltage gain of -R_c /r_e?
Fixed-bias common-emitter and voltage-divider with bypass capacitor
The most significant component of ripple voltage in a half-wave rectifier is contained in:
Fundamental frequency
A p-n junction, which is produced by recrystallisation on a base crystal, from a liquid phase of one or more components and the semiconductor is called:
Fused junction
In an intrinsic semiconductor, the mobility of electrons in the conduction band is:
Greater than the mobility of holes in the valence band
What does the negative sign in the voltage gain of the common-emitter fixed-bias configuration indicate?
The output and input voltages are 180° out of phase.
Bulk resistance of a diode is:
The sum of resistance values of n-material and p-material
A Zener diode is based on the principle of:
Tunneling of charge carriers across the junction
For a low voltage rectification:
Two diode full-wave rectifier is suitable
The reverse saturation current Is is given by:
Is ≡ AJs ≡ Ae(Dppn/Lp + Dnnp/Ln)
Oxidation in IC fabrication is used for:
Isolation
A general-purpose diode is more likely to suffer an avalanche breakdown rather than a Zener breakdown because:
It is lightly doped.
Silicon diode is less suited for low voltage rectifier operation because:
Its breakdown voltage is high
The electric field in abrupt p-n junction is:
Linear function of distance
What happens to current flow in a capacitive circuit when the DC voltage across the capacitor is approximately equal to the source voltage?
Little current flows.
The Hall Effect voltage in intrinsic silicon is:
Negative
The Hall coefficient of an intrinsic semiconductor is:
Negative under all conditions
Gold is often diffused into silicon p-n junction devices to:
None of the choices
If the energy gap of a semiconductor is 1.1 e V it would be:
Opaque to the visible light
n-type semiconductors are:
Produced when phosphorous is added as an impurity to silicon
Which of the following is NOT a primary operator used in ESPRESSO?
REDUNTANT
A NAND latch will _____when S = 1 and R = 0, and a NOR latch will _____ when S = 1 and R = 0.
RESET SET
To analyze the common-emitter amplifier, what must be done to determine the dc equivalent circuit?
Replace coupling and bypass capacitors with opens.
Which of the following is NOT the same as a Johnson counter?
Straight ring counter
If a transistor operates at the middle of the dc load line, a decrease in the current gain will move the Q point:
down
The six basic forms of energy are:
electrical, mechanical, light, heat, magnetic, and chemical
In normal operation an n-p-n transistor connected in common-base configuration has the ________.
emitter at a lower potential than the base
The depletion layer around the p-n junction in a JFET consists of __________.
immobile charges
If the secondary current in a step-down transformer increases, the primary current will ____.
increase
When ne and n_h are electron and hole densities, and μ_e and μ_n are the carrier mobilities, the Hall coefficient is positive when
n_h µ_h² > n_e µ_e²
The electron and hole concentrations in a intrinsic semiconductor are n_i and p_i respectively. When doped with a p-type material, these change to n and p, respectively. Then:
n_p = n_i p_i
For normal operation of a PNP BJT, the base must be ________ with respect to the emitter and ________ with respect to the collector.
negative, positive
One hex digit is sometimes referred to as:
nibble
One advantage TTL has over CMOS is that TTL is ________.
not sensitive to electrostatic discharge
A triangle wave consists of repeating:
positive and negative ramps of equal value
The terms "low speed" and "high speed," applied to logic circuits, refer to the ________.
propagation delay time
Doping of a semiconductor material means:
that impurities are added to decrease the resistance of the material.
You are measuring the voltage at a given point in a circuit that has very high resistance values and the measured voltage is a little lower than it should be. This is possibly because of _______.
the loading effect of the voltmeter
An SCR acts to control the speed of an electric motor by _______ of the pulse delivered to the motor.
varying the width
The Hall coefficient of sample (A) of a semiconductor is measured at room temperature. The Hall coefficient of (A) at room temperature is 4 × 10¯⁴ m³ coulomb¯¹. The carrier concentration in sample A at room temperature is:
~ 10²² m¯³
What is the current gain for the Darlington connection?
β₁· β₂
In a linearly-graded p-n junction the doping concentration:
Varies linearly with distance from junction
In a linear-graded junction, the width of the depletion layer varies as:
Vj^1/3
In a p-n diode, for constant value of current at room temperature, dv/dt varies approximately at the rate of:
-2.5 mV/°C
What are the ranges of the ac input and output resistance for a common-base configuration?
10 Ω-100 Ω , 50 kΩ -1 MΩ
What is the typical range of the output impedance of a common-emitter configuration?
40 kΩ to 50 kΩ
Which of the following best describes a zero-level detector?
A comparator with a trip point referred to zero.
A good ohmic contact on a p-type semiconductor chip is formed by introducing:
A high concentration of donors below the contact
Which of the following applications would use a photovoltaic cell?
A remote power source
The basic types of programmable arrays are made up of ________.
AND gates and OR gates
Which conditions cause the output of an XOR gate to be high?
All inputs are high.
What is the primary motivation for using Boolean algebra to simplify logic expressions?
All of the choices
What is preferably suited for applications using battery power or battery backup power?
CMOS
The transition capacitance in step-graded junction varies as:
C_jα(V_R)^-1/3
Varactor diodes are used as variable ______.
Capacitors
In a common anode, 7-segment LED display, an individual LED will light if a negative voltage is applied to what element?
Cathode
In a diode circuit, the point where the diode starts conducting is known as:
Cut-in point
The equation i_D = 0 for V_GX ≥ V_TP, represent the complete model for the i-v behavior of the PMOS transistor in which region?
Cut-off
CMOS IC packages are available in ______.
DIP and SOIC configurations
In an open circuit p-n junction, the energy band diagram of n-region shifts relative to that of p-diagram:
Downward by Eo
In a forward-biased photo diode with increase in incident light intensity, the diode current:
Increases
The Fermi energy in p-n junction at thermal equilibrium is:
Invariant with respect to distance
The width of the depletion region is:
Inversely proportional to doping
A long specimen of p-type semiconductor material:
Is electrically neutral.
The current through a p-n junction diode with V volts applied to the p-region relative to the n-region (where I₀ is the reverse saturation current of the diode, η the ideality factor, K the Boltzmann constant, T the absolute temperature and e the magnitude of charge on an electron) is:
I₀[exp(eV/ηkB T) -1]
In a semiconductor, J, J_p and J_n indicate total diffusion current density hole current density and electron current density respectively, ∂n/∂x and ∂p/∂x are the electron and hole concentration gradient respectively in x-direction and D_p and D_n are the hole and electron diffusion constants respectively. Which one of the following equations is correct? (e denotes charge of electron.)
J = -eD_p(∂p/∂x) for holes
Larger the value of the capacitor filter:
Larger the peak current in the rectifying diode
In an SCR circuit, what is the supply voltage in relation to the break-over voltage?
Less than
What do you call amplifiers that add or subtract a known voltage from the input in order to compensate for DC offset voltages?
Level shifters
Select one of the following statements that best describes the parity method of error detection.
Parity checking is best suited for detecting single-bit errors in transmitted codes.
In Monolithic IC:
Performance depends on the substrate
What is the 4-layer semiconductor diode which is equivalent to a thyristor with a disconnected gate?
Shockley diode
Measurement of Hall coefficient in a semiconductor provides information on
Sign and concentration of charge carriers
Measurement of Hall coefficient enables the determination of:
Type of conductivity and concentration of charge carriers
Which of the following is used for generating time varying wave forms?
UJT
In a transistor, collector current is controlled by:
base current
Which of the following choices meets the minimum requirement needed to create specialized waveforms that are used in digital control and sequencing circuits?
basic gates, a clock oscillator, and a repetitive waveform generator
The torque of a motor is proportional to the ________.
both amount of flux and armature current
The output of a certain voltage divider is 9 V with no load. When a load is connected, the output voltage ________.
decreases
A silicon sample is uniformly doped with 1016 phosphorus atoms/cm3 and 2 × 1016 boron atoms/cm3. If all the dopants are fully ionized, the material is:
p-type with carrier concentration of 10¹⁶/cm³
The mobility is given by (notations have their usual meaning):
μ = V₀/E₀
The conductivity of an intrinsic semiconductor is given by (symbols have the usual meanings):
σ_i = e(n_i)(μ_n + μ_p)
