52Semiconductor and Semiconductor devices

📚
CONCEPT OF ENERGY BAND IN SOLID
▢ Isolated Atom: electrons → discrete energy levels
▢ Crystal:
  • •
    atom surrounded by many atoms
  • •
    interatomic interaction → energy level modification
  • •
    outermost shell electrons → maximum effect by neighbouring electric field
  • •
    each energy level → splits into ~\(10^{23}\) closely spaced levels
  • •
    new levels → nearly continuous energy distribution
  • •
    permitted levels = no. of interacting atoms
▢ Energy Band: group of closely spaced permitted energy levels
📚
TYPES OF ENERGY BANDS
▢ Valence Band:
▢ Meaning: band containing outermost / valence electrons
▢ Energy Range: energy range of valence electrons
▢ Filling: completely filled / partially filled; never empty
▢ Current: valence electrons → unable to gain external field energy → no electric current contribution
▢ Conduction Band:
▢ Meaning: next higher band; nearly lacks electrons
▢ Filling: empty / partially filled
▢ Energy Range: energy range of conduction-band electrons = conduction energy
▢ Current: electrons gain energy from external electric field → current contribution
▢ Free Electrons: all conduction-band electrons = free
▢ Empty Conduction Band: current conduction = 0 → insulator
▢ Partially Filled: conductor
▢ Forbidden Energy Gap:
▢ Meaning: separation between conduction band & valence band
▢ Nature: empty band
▢ Symbol: \(E_g\)
📚
CLASSIFICATION OF SOLIDS IN RELATION TO ENERGY BAND
▢ Conductor:
▢ Examples: metals
▢ Conductivity: high
▢ Band Relation: valence band + conduction band overlap → no forbidden energy gap
▢ Charge Carriers: free electrons
▢ Temperature Effect: \(T \uparrow \Rightarrow\) conductivity \(\downarrow\)
▢ Fermi Level: electrons at Fermi level gain small energy → higher conduction-band level → free electrons
▢ Insulator:
▢ Conductivity: poor
▢ Valence Band: completely filled
▢ Conduction Band: completely empty
▢ Electrons: not free
▢ Forbidden Gap: large \(\approx 6\,eV\)
▢ Electric Field: large gap → electrons cannot jump VB → CB even with field → no conductivity
▢ Concept of Fermi Energy:
▢ Definition: highest energy possessed by energy-band electron at \(0K\)
▢ Fermi Level: corresponding energy level
▢ Material Dependence: different materials → different Fermi energy
▢ Conductor at 0K: occupancy probability at Fermi level = 50%
▢ Semiconductor: Fermi level = energy level with occupancy probability \(\frac{1}{2}\)
▢ Reference: used as reference energy level
▢ Semiconductor:
▢ Definition: conductivity between conductor & insulator
▢ Resistivity: \(10^{-4}\) to \(0.5\,\Omega m\)
▢ Bands: VB almost filled + CB nearly empty + small \(E_g\approx 1\,eV\)
▢ At 0K: electrons cannot cross gap → perfect insulator
▢ Room Temperature: some VB electrons gain energy → CB; ~1 electron per \(10^{10}\) atoms → little conductivity
▢ Temperature Effect: \(T\uparrow \Rightarrow\) more thermal excitation → conductivity \(\uparrow\)
▢ Temperature Coefficient: conductivity \(\propto T\); resistance coefficient = negative [KU/BPKIHS]
▢ Structure: crystalline; covalent bond
📚
TYPES OF SEMICONDUCTOR
▢ Types:
  1. Intrinsic semiconductor
  2. Extrinsic semiconductor
📖
Intrinsic semiconductor
▢ Definition: extremely pure semiconductor
▢ Examples:
  1. Si
  2. Ge
▢ Valency: 4 outermost electrons
▢ Bond: covalent bond
▢ Forbidden Gap:
❖ Si: \(1.1\,eV\)
❖ Ge: \(0.72\,eV\)
▢ Conductivity Depends On: no. of electrons transferred VB → CB; temperature dependent
▢ Free Electron Formation: thermal motion → covalent bond breakage → electron from VB to CB
▢ Current: \(I = I_e + I_h\)
▢ Carrier Equality: \(n_e = n_h = n_i\)
▢ Carrier Symbols:
❖ \(n_i\): intrinsic carrier density = free electrons or holes
▢ Conductivity: low
▢ Fermi Level: midway between conduction band & valence band
📖
Concept of hole current
▢ Hole: seat of +ve charge; charge magnitude = electron charge
▢ Creation: electron freed from covalent bond by thermal energy → missing electron site = hole
▢ Electron-Hole Pair: 1 electron freed → 1 hole created
▢ Virtual Charge: hole acts as virtual + charge; no physical charge
▢ Current Conduction: electron motion in CB + hole motion in VB
▢ Each Bond Breakage: 1 electron + 1 hole
▢ Ionization Energy Order: \(E_C > E*{Si} > E*{Ge}\)
📖
Doping
▢ Definition: deliberate addition of desirable impurity atom to intrinsic semiconductor
▢ Purpose: controlled property modification
▢ Impurity Atom: dopant
▢ Condition: dopant should not distort crystal lattice; occupies semiconductor atom position
▢ Effect: conductivity greatly increases
📖
Extrinsic semiconductor
▢ Definition: impure semiconductor obtained by doping intrinsic semiconductor
▢ Reason: intrinsic conductivity low → doping enhances conductivity
▢ Types:
  1. N-type extrinsic semiconductor
  2. P-type extrinsic semiconductor
📝
N-type Extrinsic Semiconductor
▢ Formation: intrinsic semiconductor + pentavalent impurity
▢ Dopants: Group VA: N, P, As, Sb, Bi [IOM/MOE/KU/BPKIHS]
▢ Donor Atom: pentavalent impurity donates extra electron
▢ Majority Carriers: electrons
▢ Minority Carriers: holes
▢ Carrier Relation: \(n_e > n_h\)
▢ Fermi Level: shifts toward conduction band
▢ Name Basis: majority carrier = negative electron → N-type
▢ Net Charge: no net charge
📝
P-type Extrinsic Semiconductor
▢ Formation: intrinsic semiconductor + trivalent dopant
▢ Dopants: Group III: Al, B, In, Ga etc. to Si/Ge
▢ Acceptor Atom: accepts electron from crystal lattice
▢ Majority Carriers: holes
▢ Minority Carriers: electrons
▢ Name Basis: majority carrier = positive hole → P-type
▢ Fermi Level: shifts toward valence band
▢ Net Charge: no net charge
▢ Electric Field: hole current predominant; holes move toward negative terminal
📝
Do You Know
▢ Temperature & Fermi Level: \(T\uparrow\) → Fermi level moves toward centre of forbidden gap in both types
▢ N-type Better: electron mobility > hole mobility
▢ Extrinsic Relation: \(n_e n_h = n_i^2\)
▢ Symbols:
❖ \(n_e\): electron density
❖ \(n_h\): hole density
❖ \(n_i\): intrinsic carrier density
▢ N-type Density: \(n_e \approx\) donor density \(\gg n_h\)
▢ P-type Density: \(n_h \approx\) acceptor density \(\gg n_e\)
📚
EXPRESSION FOR ELECTRICAL CONDUCTIVITY AND RESISTIVITY
▢ Extrinsic Semiconductor:
❖ Resistivity: \(\rho = \frac{1}{e(n_e\mu_e+n_h\mu_h)}\)
❖ Conductivity: \(\sigma = \frac{1}{\rho}=e(n_e\mu_e+n_h\mu_h)\)
▢ Symbols:
❖ \(\mu_e\): electron mobility
❖ \(\mu_h\): hole mobility
▢ Mobility: \(\mu = \frac{\text{drift velocity}}{\text{electric field}} = \frac{v_d}{E}\)
📖
Effect of temperature on mobility
▢ Drift Velocity: \(v_d = \frac{eE}{m}\tau\)
▢ Mobility Derivation:
  1. \(\frac{v_d}{E}=\frac{e}{m}\tau\)
  2. \(\tau \propto \frac{1}{T}\)
  3. \(\mu \propto \tau\)
  4. \(\mu \propto \frac{1}{T}\)
▢ Conclusion: \(T\uparrow \Rightarrow \mu\downarrow\); \(T\downarrow \Rightarrow \mu\uparrow\)
📚
SEMICONDUCTOR DEVICES
📖
P-n junction diode
▢ Definition: device from proper combination of P-type + N-type semiconductor
▢ Equivalent: capacitor; depletion layer = dielectric
▢ Formation Processes:
  1. Diffusion
  2. Drift
▢ Depletion Region: space charge region on both sides; immobile ions; devoid of charge carriers
▢ Diffusion:
❖ Cause: charge concentration difference
❖ Electron Motion: N-side → P-side
❖ Hole Motion: P-region → N-region
❖ Current: diffusion current
▢ Space Charge:
❖ N-side: +ve space charge
❖ P-side: -ve space charge
▢ Drift:
❖ Electric Field: field across junction
❖ Electron Motion: P-side → N-side
❖ Hole Motion: N-side → P-side
❖ Current: drift current
▢ Potential Barrier: opposes further diffusion of majority carriers
▢ Potential Barrier Values:
❖ Si: \(0.7V\)
❖ Ge: \(0.3V\)
📚
BIASING OF P-N JUNCTION
▢ Biasing: external battery connected to diode
▢ Types:
  1. Forward biasing
  2. Reverse biasing
📖
Forward biasing
▢ Connection: P-side → +ve terminal; N-side → -ve terminal
▢ Conduction: majority charge carriers
▢ Electron Motion: N-side → junction → cross junction
▢ Hole Motion: opposite direction
▢ Resistance: low
▢ Depletion Layer: size decreases [MOE]
▢ Knee Voltage: slight voltage increase beyond knee → large forward current increase
📖
Reverse biasing
▢ Connection: P-side → -ve terminal; N-side → +ve terminal
▢ Conduction: minority carriers
▢ Resistance: high
▢ Leakage Current: minority carrier current in opposite direction = leakage / reverse current
▢ Breakdown: large voltage → small leakage increase; at certain voltage reverse current abruptly increases
▢ Breakdown Voltage: Zener voltage
📝
Note
▢ Knee Voltage: forward voltage at which junction current starts rapid increase
▢ Breakdown Voltage: reverse voltage at which PN junction breaks down with sudden reverse current rise
▢ Crystal Diode: P-N junction = crystal diode
📚
P-N JUNCTION DIODE AS RECTIFIER
▢ Rectifier: device converting AC voltage/current → DC voltage/current [IOM/MOE]
▢ Types:
  1. Half-wave rectifier
  2. Full-wave rectifier
📖
Half-wave rectifier
▢ Conduction: positive half-cycle only
▢ Negative Half-cycle: suppressed; no current/voltage conducted
▢ Diode Required: single PN junction diode
▢ Output: low; AC supply delivers power half time
▢ Ripple Factor: \(\frac{I*{AC}}{I*{DC}}=\sqrt{\left(\frac{I*{rms}}{I*{DC}}\right)^2-1}=\sqrt{\left(\frac{I_o/2}{I_o/\pi}\right)^2-1}=1.21\)
▢ Form Factor: \(\frac{I*{rms}}{I*{DC}}=1.57\)
📖
Full-wave rectifier
▢ Conduction: load current same direction in both half-cycles
▢ Diodes Required: 2 diodes working alternately
▢ Power: greater than half-wave rectifier
▢ Ripple Factor: \(\frac{I*{AC}}{I*{DC}}=\sqrt{\left(\frac{I*{rms}}{I*{DC}}\right)^2-1}=0.48\)
▢ Form Factor: \(\frac{I*{rms}}{I*{DC}}=1.11\)
📖
Half-wave vs full-wave rectifier

Table 1: Rectifier Comparison

Feature
Half-wave Rectifier
Full-wave Rectifier
PN junction diode
1
2
Transformer
ordinary step-down
central tap
Conversion
half-cycle AC → DC
full-cycle AC → DC
\(I*{DC}\)
\(\frac{I_o}{\pi}=0.318I_o\)
\(\frac{2I_o}{\pi}=0.636I_o\)
\(V*{DC}\)
\(\frac{V_o}{\pi}=0.318V_o\)
\(\frac{2V_o}{\pi}=0.636V_o\)
\(I*{rms}\)
\(\frac{I_o}{2}\)
\(\frac{I_o}{\sqrt{2}}\)
\(V*{rms}\)
\(\frac{V_o}{2}\)
\(\frac{V_o}{\sqrt{2}}\)
Ripple factor
1.21
0.482
Efficiency
40.6% [IOM]
81.2%
Form factor
\(\frac{I*{rms}}{I*{DC}}=\frac{\pi}{2}=1.57\)
1.11
📖
Filter circuit
▢ Definition: circuit separating AC component from pulsating rectifier voltage
▢ Types:
  1. Choke input
  2. Shunt capacitance
  3. L-section filter
  4. T-section filter
  5. \(\pi\)-section filter
📖
Transistor
▢ Definition: semiconductor device made by sandwiching P-type or N-type semiconductor between opposite types
▢ Junctions: 2
▢ Terminals:
  1. Emitter (E)
  2. Base (B)
  3. Collector (C)
▢ Doping & Size:
❖ Emitter: thick; heavily doped
❖ Base: thin; lightly doped
❖ Collector: thick; moderately doped; physically larger than emitter
▢ Emitter: emits majority carriers → heavily doped
▢ Biasing: emitter-base junction always forward biased; collector-base junction always reverse biased [IOM/MOE]
📝
Types of Transistors
▢ P-N-P Transistor: thin N-type semiconductor between two P-type semiconductors
▢ N-P-N Transistor: thin P-type semiconductor between two N-type semiconductors
▢ Common Note: emitter-base junction → forward; collector-base junction → reverse
▢ Current Relation: \(I_E = I_B + I_C\)
▢ PNP Current: inside transistor → holes; external circuit → electrons [BPKIHS]
▢ NPN Current: inside + external circuit → electrons only [IE/KU]
📝
Transistor Connections
▢ Types:
  1. Common Emitter connection (CE)
  2. Common Base connection (CB)
  3. Common Collector connection (CC)
📝
Transistor Characteristics
▢ Input Characteristic: graph: input voltage vs input current; output voltage constant
▢ Output Characteristic: graph: output voltage vs output current; input current constant
▢ Transfer Characteristic: graph: input current vs output current; output voltage constant
📝
Amplifier
▢ Definition: electronic device converting low-voltage AC input → high-voltage AC output without changing other characteristics [MOE/IOM]
▢ Transistor Amplifier Configurations:
  1. Common base amplifier
  2. Common emitter amplifier
  3. Common collector amplifier
▢ Useful Configurations: CB and CE more useful
📄
Parameters of Common Emitter Amplifier
▢ DC Current Gain:
❖ Symbol: \(\beta\)
❖ Definition: collector current / base current
❖ Formula: \(\beta = \frac{I_C}{I_B}=\frac{\alpha}{1-\alpha}\)
▢ AC Current Gain:
❖ Symbol: \(\beta*{AC}\)
❖ Definition: change in collector current / change in base current at constant collector-emitter voltage
❖ Formula: \(\beta*{AC}=\left(\frac{\Delta I_C}{\Delta I_B}\right)*{V*{CE}=constant}\)
▢ AC Voltage Gain:
❖ Symbol: \(A_V\)
❖ Formula: \(A_V=\frac{\Delta V_o}{\Delta V_i}=\frac{\Delta I_C\times R_o}{\Delta I_B\times R_i}\)
❖ Relation: \(A_V=\beta*{AC}\times\text{Resistance gain}\) [BPKIHS]
▢ AC Resistance Gain:
❖ Symbol: \(A_R\)
❖ Formula: \(A_R=\frac{R_o}{R_i}\)
▢ AC Power Gain:
❖ Symbol: \(A_P\)
❖ Formula: \(A_P=\frac{\Delta P_o}{\Delta P_i}=\frac{\Delta I_C\times\Delta V_o}{\Delta I_B\times V_i}=\left(\frac{\Delta I_C}{\Delta I_B}\right)^2\times\frac{R_o}{R_i}\)
❖ Relation: \(A_P=\beta*{AC}^2\times\text{Resistance gain}\)
▢ Transconductance:
❖ Symbol: \(g_m\)
❖ Definition: change in collector current / change in base-emitter voltage
❖ Formula: \(g_m=\frac{\Delta I_C}{\Delta V*{EB}}=\frac{\Delta I_C}{\Delta I_B}\times\frac{\Delta I_B}{\Delta V*{EB}}=\beta\times\frac{1}{R_i}\)
❖ Result: \(g_m=\frac{\beta*{AC}}{R_i}\)
📄
Parameters of Common Base Amplifier
▢ DC Current Gain:
❖ Symbol: \(\alpha\)
❖ Definition: collector current / emitter current
❖ Formula: \(\alpha=\frac{I_C}{I_E}\)
❖ Note: \(I_C
▢ AC Current Gain:
❖ Symbol: \(\alpha*{AC}\)
❖ Definition: change in collector current / change in emitter current at constant collector-base voltage
❖ Formula: \(\alpha*{AC}=\left(\frac{\Delta I_C}{\Delta I_E}\right)*{V*{CB}=constant}\)
▢ AC Voltage Gain:
❖ Symbol: \(A_V\)
❖ Formula: \(A_V=\frac{\Delta V_o}{\Delta V_i}=\frac{\Delta I_C\times R_o}{\Delta I_E\times R_i}\)
▢ AC Resistance Gain:
❖ Symbol: \(A_R\)
❖ Formula: \(A_R=\frac{R_o}{R_i}\)
▢ AC Power Gain:
❖ Symbol: \(A_P\)
❖ Formula: \(A_P=\frac{\Delta P_o}{\Delta P_i}=\frac{\Delta I_C\times\Delta V_o}{\Delta I_E\times V_C}=\left(\frac{\Delta I_C}{\Delta I_E}\right)^2\times\frac{R_o}{R_i}\)
❖ Relation: \(A_P=\alpha*{AC}^2\times\text{Resistance gain}\)
▢ Transconductance:
❖ Symbol: \(g_m\)
❖ Definition: change in collector current / change in emitter-base voltage
❖ Formula: \(g_m=\frac{\Delta I_C}{\Delta V*{CB}}=\frac{\Delta I_C}{\Delta I_E}\times\frac{\Delta I_E}{\Delta V*{EB}}=\alpha*{AC}\times\frac{1}{R_i}\)
❖ Result: \(g_m=\frac{\alpha*{AC}}{R_i}\)
📃
Do You Know
▢ CB Amplifier Phase: input signal voltage & output voltage → same phase; phase difference \(0^\circ\) [MOE]
▢ CE Amplifier Phase: input signal voltage & output collector voltage → phase difference \(180^\circ\) [BPKIHS]
📄
Relation Between DC Gain in CB and CE Amplifiers
▢ Current Relation: \(I_E=I_B+I_C\)
▢ Gain Relations: \(\alpha=\frac{I_C}{I_E}\), \(\beta=\frac{I_C}{I_B}\)
▢ Derivation:
  1. \(\frac{I_E}{I_C}=\frac{I_B}{I_C}+1\)
  2. \(\frac{1}{\alpha}=\frac{1}{\beta}+1\)
▢ Conclusion: \(\beta>\alpha\) [IOM/MOE/KU/BPKIHS]
▢ Notes:
  1. \(\beta*{AC}>\alpha*{AC}\) → voltage gain & power gain in CE > CB
  2. \(\alpha\) range: 0.8–0.9
  3. \(\beta\) range: 20–200
Q1.
In diode when current flows from P to N it is called
📅MOE 2010
Q2.
A certain glass of material with a wide forbidden band between the valence and conduction bands is called
📅MOE 2012
Q3.
Zener diode are used for
📅BP 2017
Q4.
When antimony is doped with silicon, extrinsic semiconductor obtained is
📅MOE 2010
Q5.
The silicon semiconductor formed by doping trivalent atoms will be
📅MOE 2009
Q6.
The energy gap between the conduction band and the valence band of a certain material is 0.7eV. The material is
📅KU 2009
Q7.
What is voltage gain in a common emitter amplifier, where input resistance is 3Ω & load resistance 24Ω, β = 0.6?
📅BP 2009
Q8.
In npn transistor, electron move from
📅BP 2011
Q9.
Voltage gain of amplifier depends on
📅BP 2012
Q10.
Electrical conductivity of semiconductor of this type increases with increase in temperature:
📅I.E 2012
Q11.
Which of the following is doped with silicon to form N-type semiconductor?
📅I.E 2012
Q12.
When P-N junction diode is forward biased;
📅I.E 2012
Q13.
If the temperature of a semiconductor is lowered from T1 to T2. The resistance of semiconductor
📅I.E 2012
Q14.
To a silicon sample traces of aluminium are added as an impurity. The resultant sample would behave like:
📅I.E 2010
Q15.
In which of the following transistor amplifier configurations, the voltage gain is highest.
📅I.E 2010
Q16.
The current gain in a transistor is 0.98. If the change in emitter current is 5mA. The change in collector current is:
📅I.E 2011
Q17.
Which of the following shows forward biasing?
📅I.E 2009
Q18.
Which is correct for a transistor?
📅KU 2010
Q19.
When p-n junction diode is forward biased the width of depletion layer.
📅MOE 2008
Q20.
The impurity atoms with which pure silicon should be doped to make an n-type semi-conductor is:
📅MOE 2062
Q21.
Silicon and silver both are cooled from 100°C to 0°C, their conductivity changes as
📅MOE 2055
Q22.
For proper use of a transistor:
📅MOE 2053
Q23.
A device for generating an Alternating current of a desired frequency is known as
📅T.E. 2004
Q24.
The potential barrier in the depletion layer is due to
📅T.E. 2008
Q25.
In a semiconductor diode P-side is earthed and N side is applied a potential of -2V the diode shall
📅BPKIHS-07
Q26.
Forbidden energy gap shows the order
📅BPKIHS-02
Q27.
In a PN junction diode, when no potential is applied
📅BPKIHS-02
Q28.
A transistor is essentially a:
📅BPKIHS 05
Q29.
When P-N junction diode is forward biased and then reverse biased the flow of current is mainly due to
📅BPKIHS 2000
Q30.
The resistivity of semi conductor depends on
📅BPKIHS-06
Q31.
Which of the following is correct?
📅BPKIHS-06
Q32.
A N-P-N transistor in a common emitter circuit has
📅BPKIHS-94
Q33.
The drift current in a P-N junction diode is
📅BPKIHS-97
Q34.
Comparison of conductivity of Ge and Cu when temperature falls from 25°C to 80 K
📅BPKIHS 98
Q35.
Ge transistor can be operated at a temperature
📅BPKIHS 98
Q36.
The ratio of electron and hole current in a semiconductor is 4/3 and the ratio of drift velocities of electron and holes is 2/3, then the ratio of concentration of electrons and holes will be
📅BPKIHS 98
Q37.
If a semiconductor has an intrinsic carrier concentration of 1.41×1016/m³ when doped with 1021/m³ phosphorous atoms, then the concentration of holes/m³ at room temperature will be
📅BPKIHS 98
Q38.
The depletion layer in silicon diode is 1µm wide and the knee voltage is 0.6V, the electric field in the depletion layer will be.
📅BPKIHS 98
Q39.
Consider the junction diode is ideal. The value of current in the circuit is
📅BPKIHS 98
Q40.
A n-p-n transistor circuit has α = 0.984, if IC = 2mA, then value of IB is
📅BPKIHS 98
Q41.
The electrical conductivity of semiconductor
📅BPKIHS 98
Q42.
An n-type semiconductor is
📅BPKIHS 98
Q43.
An electric field is applied to semiconductor. Let the number of charge carriers be n and the average drift speed be v. If the temperature is increased.
📅BPKIHS 98
Q44.
Diffusion current in a p-n junction is greater than the drift current in magnitude if
📅BPKIHS 98
Q45.
The dominant mechanism for motion of charge carriers in forward and reverse biased silicon p-n junction are:
📅BPKIHS 98
Q46.
In a good conductor, energy gap between the conduction band and valence band is
📅BPKIHS 98
Q47.
In an n-p-n transistor circuit, the collector current is 10mA. If 90% of the electrons emitted reach the collector
📅BPKIHS 98
Q48.
When the conductivity of a semiconductor is only due to breaking of covalent bond, the semiconductor is called.
📅BPKIHS 98
Q49.
Filter circuit
📅BPKIHS 98
Q50.
Current gain of a transistor in common base model is 0.95. Its value in common emitter mode is
📅BPKIHS 98
Q51.
The current gain of a transistor in a common emitter configuration is 40. If the emitter current is 8.2 mA, then base current is
📅BPKIHS 98
Q52.
For a common base amplifier, the values of resistance gain and voltage gain are 3000 and 2800 respectively. The current gain will be
📅BPKIHS 98
Q53.
The value of current in the following diagram will be
📅BPKIHS 98
Q54.
The forward bias diode is
📅BPKIHS 98
Q55.
Which of the following semiconductor diodes is reverse biased?
📅BPKIHS 98
Q56.
In an NPN transistor the collector current is 24 mA. If 80% of electrons reach collector, the base current is
📅BPKIHS 98
Q57.
Mercury is cooled to 4K, it behaves as
📅IOM 2016
Q58.
When intrinsic semiconductor is doped with impurity then conductivity is:
📅KU 2016
Q59.
Forward biasing of p-n junction offers:
📅KU 2016