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PHY301 Circuit Theory-final term exam feb 2012
Why is electron flow with the arrow in the symbol of a Zener diode instead of against the arrow as it is in a normal diode?
In zener diode the differential voltage and current in the zener region of the characterist curve is given as
datla V = Rz Dalta I
Diode:
A diode will conduct when it meet the condition that the voltgae difference between the anode and the cathode exeeds the the barrier voltage of approximately 0.3 volts for a gemanium diode and .07 of silocon diode.
When positive termianal of a battery is connected to the anode and negitive terminal to the cathod of a diode the diode is said to be forward biased.
When positive terminal of a batter is connected to the cathode and negitive terminal to the anode the diode is said to be reversed biased.
What resistance property is found in tunnel diodes but not in normal diodes?
The Tunnel diode are used in vulta high frequency and microwave frequency range. They have appication in hight frequency communication electronics.
Using the Thevenin's theorem, what type of changes we will do in the circuit, to find Thevenin’s voltage Vth? No need to solve the circuit.
State Kirchhoff’s voltage law (KVL).
Kirchhoff's Voltage Law,
The law states that the algebric sum of the voltage aroung any loop is zero.
Or
sum of voltages rises and voltage drops aroung any closed path or loops is equal to zero.
What is the dependence of junction area and temperature of pn junction diode on Leakage current?
The leakage currents are proportional to the junction area just as Is.its Dependance on the temperatur is however different from that of Is.
Consider the circuit as shown, Write Vs equ. for AC analysis purposes.
Define Ohm, s law and its formula in various forms.
Ohm's Law,
If a voltage across a conductor is applied, the current passing through the conductor is directelly proportional to the voltage
V X I
V=IR
Where R is reisitance of the conductor Which depends upon the material of the conductor.
Farmula in Various Forms
I = V / R
&
R = I / V
Describe the function of transistor.
Transistor:
It is Three layer simiconductor device consisting of either two n and on p type layers of material of two p and one n- type layers. Three layer are involved in the device there for it wll have thre terminal these terminal are knows are Emitter, base Collector.
Emitter,
This layer emit electrons
Base,
It helps minority carries to transfer rapidly from emitter to collector.
Collector,
This layer collects the Emitter electrons
Describe the basic circuit operation of this rectifier for +ve half signal.
Just draw circuit in order to find Thevenin’s resistance Rth,no need to calculate value.
What is the difference between Ideal diode model and practical diode model?
Ideal Diode model,
We know that the diode behaves essentially as swithc. On when forward biased off when reverse based. The ideal diode characteristic are when the diode is reverse biased we replact it with and open switch and when the diode is forward bised we use a closed switch
Practial diode model,
There is a voltage drop of avout .07 V accross the diode when it is forword biased and so it is often useful to include theis voltage drop in circuit analysis according the practical model is the ideal model with the addition of a voltage source in the forward bise model.
Trace the current through this rectifier circuit at a moment in time when the AC source's polarity is positive on left and negative on right as shown. Be sure to designate the convention you use for current direction (conventional or electron flow):
Also, mark the polarity of the voltage drop across Rload.
First Identify and label each node in the network. Write constraint equation and super node equation for the given circuit.
Given below are two figures (a) and (b) having Diode, which diode is forward biased or reversed biased? tell reason.
Both A and B are reversed biased.
In figer A the negative of the batter is connected to the anode through a resistor and positive termianl of the battery is connected the cathode therefore no current ll flow and we cansay that diode is not existing and it ll act as and open circuit.
In Figer b the negative terminal of the battery is connected to the anode through a resistor and positive terminal of the battery is connected the cathode
Differentiate between Clippers & Clampers. Also write the various types of Clipper circuits and define each type.
Differentiate between Clippers & Clampers. Also write the various types of Clipper circuits and define each type.
Clippers,
There are varity of diode networds call clippers that have the ability to clip off a portion of the input signal without distortiong the remaining part of the alternativing waveform. The half wave rectifier studied earlier is a simplest form of diode clipper. Depending on the orientation of the diode the positve or negative region of the input signal is clipped off.
It makes a sketch in mind about the response of the network.determine the applied voltage that causs change in the diode bise. be continuously aware of the difined terminal and porlarity of Vo. Sketch the input signal on the top and the output at the bottom to determine the output at instantaneouse pointer of the input.
Types of Clipper,
There are two general types
Series
The series is defined as one where the diode is in series with the load as half wave rectifier.
Parallel
The parellel is the one where the diode is in parallel wiht the load as half wave rectifier.
Clampers,
There are the circuits which clamps the input signal to a different level depending upon the configuration of the clamper circuit.
Tags: 2012, Circuit, PHY301, Theory-final, exam, feb, term
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PHY301-2012-paper.pdf, 398 KB
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