Piletid vastustega (2)

Ticket No1
1)The characteristic is called output characteristic or volt-ampere charateristic of a Rectifier Diode .
2)Rectifier Diode .
3)A is called Anode and C is called Cathode. An Anode has positive potential and therefore collects electrons in the device . Cathode has negative potential and therefore emits electrons to anode. The symbol looks like an arrow that ponts from the anode to the cathode, and reminds that conventional current flows easily from the p side(anode) to the n side(cathode).
BIASING.
Forward biasing. If the current in a diode is too large, excessive heat will destroy the device. Even approaching the burnout current value without reaching it can shorten its life. Therefore manufacturer’s data sheet specifies the maximum forward current, that diode can withstand. This average current IF is the rate a diode can handle up to the forward direction when used as a rectifier. Another entry of interest in the data sheet is the forward voltade drop UF(max) when the maximum forward current occurs. An usual diode has this value 0.7-2.0V. Diode conducts easily when forward biased .
Reverse biasing. The reverse current is a leakage current at the source rated voltage . Typically, silicon diodes have 1-10 microA and germanium 200-700 microA of leakage current. This value includes thermally produced current and surface leakage current. Only these currents take place , when a diode is reverse biased. At breakdown, the diode goes into avalanche where a number of carriers appear suddenly in the depletion layer . With a rectifier diode, breakdown is usually destructive.
4) Typical values : Uknee- approximatly 0.7V; UF – 0.7-2.0V; leakage (IR) – 1-10 microA/200-700microA.
5)Idealized characteristic. In view of a very small leakage current in the reverse- bias state and a small voltage drop in the forward-bias state as compared to the operating voltages and currents of a circuit in which the diode is used, the oputput characteristic of the diode can be idealized as shown in the figure . This corner can be used for analyzing the circuit topology, but should not be used for actual circuit design. At turn on, the diode can be considered as an ideal switchbecause it turns on rapidly as compared to transients in the circuit.
6) One of its main applications is in rectifiers, circuits that convert the Alternating voltage or alternating current into direct voltage or direct current. It is also applied in detectors, which find the signals in the noisy operation conditions . The third application is in switching circuits because an ideal rectifier acts like a perfect conductor when forward biased and lik a perfect insulator when reverse biased.
7)A power diode is more complicated in structure and operational characteristics than the small signal diode. The forward bias characteristic of the power diode is approximately linear , which means that the voltage drop is proportional to the omic resistance and to the current. The rated currents of power diodes are thousands of amperes and the area of the pn junction may be tens of square centimeters.
In the case of power diode, the additional n- layer exists between these two layers, which is termed as a drift region . This layer can be quitewide for the diode. The wide lightly doped region adds significant ohmic resistance to the forward-biased diode and causes larger power dissipation in the diode when it is conducting current.
Most of the power dissipation in a diode occurs in the forward-biased on-state operation. Real poeration currents and voltages of power diodes are essentially restricted with power losses and the thermal effect of power dissipation. Therefore, in power devices cooling is very important.
In the case of reverse biased voltage, only the small leakage current flows through the diode. This current is independent of the reverse voltage until the breakdown voltage is reached. After that, the diode voltage remains essentially constant while the current increases dramatically.Only the resistance of the external circuit limits the maximum value of current.
8)For power diodes, switching process is the most common operation mode. A power diode requires a finite time interval to switch over from the off-state to the on-state or vice versa. Switching properties are analyzed at a given rate of current change .
The most essential data of power switching are the forward voltage overshoot(UF(max)) when a diode turns on and the reverse current peak value(IR(max)) when a diode turns off.
If Ploss=0, the efficiency is approx. Equial to 25% 50% 75% 100%
What are the sources of current? carriers electrons neutrons protons
Ticket No 2
Varactor Zener diode Bi-directional diode Schottky
LED Photodiode Optocoupler(LED and photo )
2, 3, 4)Varactor. Zener. Bi-directional.Sch.Led.
Photodiode.
5)Varactor: U=1-100V, C=10-100 microF. Zener: Zener=-2.4...-200V. Schottky: on state voltage drop=0.3V. LED: conducting current=2- 10mA .Voltage drop=2-3V.
6)Varactor: +( higher reverse voltage, smaller capacitance) Bi-direct:+(it operates in either direction to monitr under-voltage dips and over-voltage spikes of the ac input) Schottky:+(high frequency , very fast ) –(Very low breakdown) LED:+(Low voltage, long life, fast switching)
7)Zener: designed to operate in the reverse breakdown. They are backbone of voltage regulators.Bi-directional:Used for line filtering . Two Zener diodes connected back -to-back. It is used as a filtering device to protect voltage- sensitive electronic devices from high-energy voltage transients.Schottky: High frequency diode. Based on the fact , that electrons in different materials have different absolute potential energies and the potential energy of electrons in materials is lower than the potential energy of the free electrons. Used in computers, because of the speed .LED:Energy is radiated as light .(in other diodes as a form of heat). Emits visible and invisible light rays when forward current through it exceeds the turn-on current.Used in lamps. Photodiodes:A window lets light pass through the packageto the junction. The incoming light produces free electrons and holes . The stronger the light, the greater the number of minority carriers and the larger the reverse current. Optocoupler: LED on the input side and photodiode on the output side. Light from the led hits the photodiode and this sets up a reverse current in the output circuit.
8)
How many valence electrons a germanium atom has? 1 2 4 8
How is it called the n-type semiconductor ? donor recipient acceptor dipol
Ticket No3
1,2) Collector characteristic(output characteristics) and input characteristic of Bipolar Junction Transistor (BJT)
3)A junction transistor has three doped regions . The bottom is the emitter, middle is base and top is collector.A transistor has two junctions on opposite sides of a thin slaf of semiconductor crystal :one between the emitter and the base and another between the bas and the collector. Transistor is similar to two back-to-back connected diodes. For normal operation, the emitter diode is forward biased and the collector diode is reverse biased.(Reverse biased) (Schematic symbols of npn&pnp).Three different currents: IE,IB,IC.
5)(Common emitter, Common base, Common collector.)A:Common emitter input signal drives the base whereas the output signal occurs between the collector and the emitter. It is the most popular circuit because of its high flexibility and gain .B:Common base input signal drives the emitter whereas the output signal occurs between the collector and the base. This connection is known as low-gain circuit with high frequency selectivity Q. C:Common collector input signal drives the bae, and the output signal comes from the emitter.
7) Beta :The ratio of the collector current IC to the base current IB is called a current gain or a static gain or dc beta of a transistor and is expressed as β=IC/IB. This parameter is also called a forward-current transfer ratio. It is the main property of the transistor in the CE connection. The current gain of a transistor is an unpredictable quantity and may vary as much as a 3:1 range when changing in the temperature, the load , and from one transistor to another. Alpha :the dc alpha of a transistor indicates how close in value the collector current and the emitter current are.It is defined as:α=IC/IE.Alpha gain is the main property of the transistor in the CB connection. Consequently,a formula of alpha gain in terms of beta is: α=β/(β+1). Alpha gain is always less than 1 and is near 1. Both gains depend on the signal frequency.In the data sheets, the limit frequency is shown, which reduces dc beta to 1.
8)Devices used in power applications are called Power Bipolar Transistors.Small signal transistors can dissipate half a watt or less. Power transistors dissipate more values.This rating is the limit of the transistor currents, voltages and other quantities,which are much higher than those of small-signal devices.In mos applications, power bipolar transistors are used in a CE circuit with the base as an input and the collector as output.In power electronic circuits bipolar NPN are more common than PNP.The base thickness must be made as small as possible in order to have a high amplification effect, but too small base thickness will reduce the breakdown voltage capability.The allowed max voltage UCE between the collector and the emitter depends slightly on the base current. Since the current gain of power bipolar transistors is small, two transistors are usually connected as a pair .It’s called Darglington transistors.The emitter of the first transistor is connected to the base of the second one.A connected pair of bipolar transistors could raise the current gain of a power device.The difference between power and low current transistors is, that power transistors have primary and secondary breakdown area in output characteristics.After primary breakdown, the transistor can operate, but the secondary breakdown destroys the transistor completely.As a result , a narrow safe operating area is the remarkable disadvantage of the transistor.
If Pin = Pout, the efficiency is approx. equal to: 25% 50% 75% 100%
How many electrons a silicon atom has? 8 14 24 32
Ticket No4
1,2)A:Junction Field-Effect Transistor ( JFET ) output characteristic.B:Input curve of a JFET.C:Transconductance curve of Metal -Oxide Semiconductor Field-Effect Transistor(Depletion mode- MOSFET ).D:Input curve of enhancement-mode MOSFET.
3)JFET:MOSFET:Enh-modeMOSFET:
4)JFET:Lower lead is called source, and the upper lead is the drain.To produce a JFET,two areas of a p-type semiconductor into the n-type semiconductor have been diffused.Each of these p regions is called a gate .Most JFETs have the two gates joined internally to achieve a single external gate lead, tuhus the device acts, as though it has only a single gate.In JFET the gate-source diode is always reverse biased.Because of this, only a very small reverse current can exist in the gate lead.
Depletion-modeMOSFET: Figure shows a structure and a way to bias an n- channel depletion-mode MOSFET with a p-region called a substrate.In its most basic form, the mosfet looks like a voltage-controlled resistor , the resistance of which varies nonlinearly with the input voltage.In the on-state, tis resistance can be less than 1ohm, while in the off-state, the resistance increases to several hundreds of megaohms, with picoampere leakage currents.
Enhancement-mode MOSFET:When the gate voltage is positive enough, electrons fill all the holes touching the silicon dioxide. The effect is the same as creating of a thin layer in n-type material next to silicon dioxide.This conducting layer is called an n-type inversion layer.The normally of device suddenly turns on and free electrons begin to flow easily from the source to the drain.
5)Unlike JFET, MOSFETs metallic gate is electrically insulated from the channel by a thin layer of silicon dioxide.Because of this, the input resistance is evene higher than that of a JFET.Ability to use a positive gate voltage distinguishes MOSFET from JFET.Depletion mode MOSFET has an n-channel between the source and the drain. Enhancement-mode MOSFET doesn’t have an n channel.And also enhancement-mode MOSFET is normally off when the gate voltage is zero , whereas a depletion-mode device is normally on.
6)Advantages of JFET:a)Due to the voltage adjustment, the control circuit is simple with a low control power;b)because a JFET is an electron majority carrier device, the switching transients speed grows essentially;c)for some reason , its on-state resistance has a positive temperature coefficient, that is the resistance rise with the temperature rise;d)accordingly, the current falls with the load and the parallel connection of such devices is not the problem;e)due to the absence of the second breakdown, the safe operating area is large, therefore the overvoltage protection is not needed. Disadvantages :a)due to the high transistor resistance of the current flow, the efficiency of FET is not high when a number of transistors are connnected in parallele;b)the additional losses between the source and the drain complicate the control processes.Advantages of MOSFETs:a)high speed switching capability, that is the operational frequencies up to 10GHz with the transient speed 10-100ns because of almost no saturation ;b)switching of positive and negative voltages and conducting of positive and negative currents with equal ease ;c)simple protection circuits;d)simple voltage control;e)normally off device if the enhancement-mode MOSFET is used;f)positive temperature coefficient makes it easy to be applied for parallel devices for increased current- handling capability.Disadvantages:a)relatively low power handling capabilities(less than 10kVA, 1000V , and 200A);power losses are proportional to the square of current value.b)relatively high(more than 2V) forward voltage drop, which results in higher losses than BJT.
7)ID(max)=2-50A;UDS=60-500V,UG(max)=+/- 20V
8)Power enhancement-mode MOSFET.The structure of a semiconductor is composed of many thousands of cells connected in parallel to achieve a large gain and low on-state resistance. Overall , the input curve of a power MOSFET is quite linear compared with the parabolic transfer curve of a small-signal MOSFET.Threshold voltage is 2-4V. Double -diffused transistor(DMOS) is a kind of a power MOSFET.The device is fabricated on a lightly doped n-type substrate with a heavily doped region at the bottom for drain contact.Two diffusions are used, one to create the p-type body region and another to created n-type source region.Breakdown voltage up to 600V and current capability up to 50A.
How many electrons a germanium atom has? 8 14 24 32
Holes are the minority carriers in which type of semiconductor? n-type p-type each never
Ticket No5
1)Insulated Gate Bipolar Transistor (IGBT)
2,3)OutputcharacteristicsInput characteristics
Typical graphs of collector current versus frequency.
4)IC(max)=30- 600A ;UCE=120-1200V
5)Structure is quite similar to enhanced-mode MOSFET.The principal difference is the presence of p layer that forms the collector of the IGBT.This layer arranges the pn junction which injects minority carriers.
6)
7)Advantages:a)the highest power capabilities up to 1700 kVA,2000V,800A;b) thanks to the lower resistance than that of the MOSFET,the heating losses of the IGBT are low too;c)highest switching capabilities;d)forward voltage drop is 2-3V, that is higher than that of a bipolar transistor but lower than that of the MOSFET;e)relatively simple voltage controlled gate driver and low gate current;f)the reliability is higher than with the FET thanks to the absence of a secondary breakdown.
8)The leading manufacturer of IGBTs International Rectifier classifies the production by the four categories:1)“W“-warp speed devices for 17 to 150kHz;2)“U“-ultra fast speed devices for 10 to 75kHz;3)“F“-fast speed devices for 3 to 10kHz;4)“S“-standard speed devices for 1 to 3kHz.
If Ploss = Pin, the efficiency is approx. equal to: 25% 50% 75% 100%
Atomic number is equal to the number of: carriers electrons neutrons protons
Ticket No6
1,2)Output characteristics of Thyristors.
3)A silicon-controlled rectifier(SCR) consists of a four-layer silicon wafer with three pn junctions.It has four doped regions;the anode,the cathode, and the gate.The gate is the control lead.The SCR is triggered into conduction by applying a gate-cathode voltage, which causes a specific level of gate current.When the SCR is turned off, it stays in a non-conducting state until it recieves another trigger.Therefore the SCR can be termed as one-operation thyristor or rectifier thyristor.B)the anode-side SCR with an n-gate lead.C)the cathode-side thyristor with a p-gate lead.C)most common device.
5)Input characteristic:The curves show the relation between the gate current and the gate voltage.This relation has a broad coherence area with a width that depends on the temperature and design properties of the device.The gate current has an effect upon the form of the characteristic.The value of a breakover voltage is the function of the gate current. The more the gate current, the lower level of voltage is required to switch on the thyristor.
6)Figure reflects the current and voltage transients of a thyristor when it turns on after a gate pulse appears and turns off after the current direction changes . During the thyristor opening process, the anode current will be distributed through the full crystal surface.The current distribution is not homogeneous.The turn-on process includes three time intervals:the turn on delay t0, the current rise time t1 and the current spreading timet2.The turn-off process is similar to the diode.For that, the anode current must be kept well below the hold current.The decreasing rate of the current depends on the circuit inductance.The density of excess carriers will diminish by the recombination.
7)Diac is a bi-directional diode that can be triggered into conduction by reaching a specific voltage value.The diac can pass current in either direction.This is the current-voltage characteristic.A diac has neither an anode, nor a cathode.Its terminals are marked as MT1(main terminal1) and MT2(main terminal2).
Triac(bi-directional thyristor) is a three terminal five-layer device capable of conducting current in both directions. It is identified as a three electrode ac semiconductor switch that switches conduction on and off during each alternation .its terminals are:MT1;MT2 and G(gate).
8)Triacs can operate in power modes of 1,5kV and 100A.
If Ploss = Pout, the efficiency is approx. equal to: 25% 50% 75% 100%
If a transistor has an emitter current of 10mA and a collector current of 9,95mA, what is the base current (A)? 0,05 19,95 50 19950
Ticket No7
1)Emitter-follower.2)The base ac voltage produces an emitter ac current.Thanks to the limiting resistor RB and the coupling capacitor CB, an ac voltage appears at the emitter.The biasing is arranged with the help of R1 and R2.Because of the output capacitor C, this voltage is coupled to the load.Since the emitter is no longer at ac ground , the ac voltage across the emitter is approximately equal to the input voltage at the base.The reason the circuit is called an emitter follower is because the output voltage follows the input voltage.
3)
4)current,ac,feedback.5)analog, class A
6)
7)ADVANTAGES:The output impedance is significantly lower than the inpud impedance.That is, the circuit is especially useful to decrease the output resistance of the electronic device.Another benefit is, that almost no distortion of the signal occurs.That is why the emitter follower is often used as an intermediate stage of a power amplifier for current amplification.DISADVANTAGES:high noise and limited frequency range, over which the stabilization is effective.Phase delay.DC stops.Additional area, volume, size , weight of amplifiers.
8)
If Vrms = 10, then Vpeak-to-peak sin is approx. equal to: 10 30 60 90
What is the current gain with an input current of 5A and an output current of 10mA?
2 50 2000 5000
Ticket No8
1) Differential amplifier, or diff amp circuit.2)
3)Figure presents a general form of a diff amp that is termed a long-tailed pair because RE is called a tail resistor.It has two inputs:U1 and U2.Because there are no coupling or bypass capacitors, the input signals can have frequencies all the way down to zero, equivalent to dc, and the amplifier has a broad midband and high stability.The output signal is the voltage on the load connected between the collectors.Ideally, the circuit is symmetrical with identical transistors and collector resistors.
4)dc,voltage device.5)analog.
6)ADVANTAGES:Because there are no coupling or bypass capacitors, the input signals can have a wide range of frequencies and the amplifier has a broad midband and high stability.Other benefits are high amplification and low clipping.MAIN FEATURES :Signal range,offset and drift,kind of supply .
7)To obtain higher voltage gain of an amplifier,one can connect two stages.This is called cascading of the stages and means the amplified voltage out of the first transistor is coupled into the base of the second transistor.The second transistor then amplifies the signal, so that the signal is much higher than the input signal.
Ticket No9
1)Schematic diagram of the operational amplifier(op amp).2)The input stage is a diff amp using pnp transistors T1 and T2. T6 forms an active load that replaces the tail resistor.R2 and D2 control the bias on T6 which produces the tail current of the diff amp.Instead of using an ordinary resistor,the active load T3 is used.Because of this, the voltage gain of the diff amp is high.The amplified signal from the diff amp drives the base of T4,which is and emitter follower.This stage avoids the loading down of the diff amp.The signal out of T4 goes to T5.Diodes D4 and D5 are part of the biasing for the final stage.T7 is an active load for T5.Therefore, T5 and T7 are like a CE stage with a very high voltage gain.The amplified signal of the CE stage goes to the final stage,which is a class B emitter follower T8 and T9.Thanks to the balanced supply,the output is 0V when the input voltage is zero.
3)The input signal determines the output voltage swing requirement of the op amp.There are a number of single-supply amplifiers with inputs that range from 0V to the positive supply voltage.However,the input range can be set so that the signal only goes to within a few hundred millivolts of each rail.In many single-supply applications it is required that the input common-mode voltage range extends to one of the supply rails.
4)dc, voltage,feedback.
5)analog
7)FEATURES:high gain, high input resistance,low output resistance,controlled bandwidth extended to dc.ADVANTAGES:high frequencies,direct coupling.
8)
How many electrons are there in the valence orbit of a silicon atom within a crystal? 8 14 24 32
What is the current gain of a bipolar transistor? IC/IB IE/IB IC/IE IE/IC
Ticket No10
1) Left one:Frequency response of passive low-pass filters ;Second:Frequency response of passive high-pass filters;Third:Frequency response of passive band -pass filters;Right:Frequency response of passive band-stop filters.2)Filters.
3)Circuit diagram for Low-pass filters:RC&LC:Passive high-pass filters:
Passive band-pass filter :Passive band-stop filter:
4)
5)Low-pass filter reduces high-frequency particles of a signal and passes its low frequency part.High-pass filter is open for high frequencies and attenuates the low-frequency signals.Band-pass filter:at very low frequencies, the series capacitor looks open to the input signal and there is no output signal.At very high frequencies,the shunt capacitor looks short circuited,and there is no ouput also.In between these extremes,the output voltage reaces maximum value at the resonant frequency.Band-stop filter:circuit with almost zero output at the particular frequency and passing the signals, the frequencies of which are lower or higher than the cutoff frequencies.
6)
7)low-pass&high-pass: fc=1/(2πRC);fc=1/(2πSQRT(LC)) band-pass:fr=1/(2πSQRT(L1C1)) or fr=1(2πSQRT(L2C2)):f2-f1=R/(πL1)=1/(πC2R). band-stop: f2-f1=R/(4πL2)=1/(πC1R)
8)
If Vpeak-to-peak sin = 100, then Vrms is approx. equal to: 10 30 60 90
When is the atom said to be in electrical balance?
electrons=protons electrons=holes electrons=carriers carriers=holes
Ticket No11
1,2)Left:op amp suming amplifier( summer or adder);Second:Integrator;Third:Differentiator;Right:Proportional- integrated -differential circuit(PID).
3)
4)input and output signals are on the circuits.5)summer:the output is the sum of the input voltages.Integrator:produces a ramp of output voltage,which is a linearly increasing or decreasing voltage.Differentiator:produces an output voltage proportional to the instantaneous rate of change of the input voltage.PID:They amplify the beginning and the end of the pulse signal.6)Summer:Uout=-(U1R/R1+U2R/R2+U3R/R3).Integrator:Uout=-1/T int(Uindt);Iin=Uin/R;Uout=-Iint/C = -Uint/T;Uout= -Uin/(4fT).Differentiator:Uout= -T dUin/dt.PID:K=R2/R1;T1= R1C1 ;T2=R2C2
7)Substracter:The output voltage,which is proportional to the difference of the input voltages when R1=R2 and R=R3.
Logarithmic:It is the inverting amplifier with a feedback diode rather than feedback resistor. Once the diode and the resistor positions replace on other, the exponential amplifier appears:
In case of the positive feedback, the midband becomes: larger narrow no matter no band
What is the main action of electrons in the base of an npn transistor? recombination flowing -out doping ionization
Ticket No12
1,2)Switches(switching circuits).Left: Inverter ;Second:Multiplexer;Third:Comparator;Right: Latch .
3)Switching devices. 4)Switching transistor circuits are known as class B operation devices.It means, that the collector current flows only one half of ac.For this to occur, the Q point is located at cutoff on both the dc and ac load lines. Transistors are, because transistorized base bias is usually designed to operate in switching circuits by having either low output voltage or high output voltage.5)on circuits.6)Inverters output voltage is in the opposite polarity to the input voltage.Multiplexer is a multiple switch that steers one of the input signals to the output.Comparator:perfect solution for comparing one voltage with another to see which is larger.Latch:because the collector of T1 drives the base of T2 and vice versa,it is a positive feedback.Achange in current at any point of the loop is amplified and returned to the starting point with the same phase.
7)Advantages of swithces:Extremely low power consumption and lower heat production.Physically small.They can provide large load currents at low voltages although they produce more electrical and audible noise.Adv of comparator:fast differential dc amplifier of high gain and stability.Disadv:need high resolution which implies high gain.
8)Sample-and-hold circuit(SHA)It captures an analog signal and holds it during some operation.When the SHA is in the hold mode, the output is closed.When the SHA is in the sample mode, the output follows the input with a small offset equal to the hold period.The energy storage device, the heart of the SHA is acapacitor.
RS flip - flop :Each collector drives the opposite base through a resistors RB.One transistor is saturated and the other is cutoff.Depending on which transistor is saturated,the Q output is either low or high.RS flip-flo circuit can set the Q point to high or reset it to low.High input S sets Q to high and high input R resets Q to low.
What does the electron interact with? hole neutron dipole crystal
What does the flowing of electrons in an npn transistor start from? emitter collector base gate
Ticket No13
1)Oscillators.2)Left: Push - pull amplifier;Second:RS flip-flop;Third:Blocking oscillator;Right:Astable multivibrator.
3)Switching. 4)Left one: Class B transistors. Pair of identical Transistors are there to reduce disortion.So that the signal can be introduced across.Right one:The input of the first transistor amplifier is the output of the second one.Once the current of one transistor becomes higher the other,the voltage drop of its collector’s resistor grows.This change is transferred through the corresponding capacitor to the base of the other transistor so that the current grows increasingly up to the first transistor saturation and the second transistor closing .Third one:Originally, the forward biased transistor emits the base of the transistor.The capacitor charges and sends the pulse to the transformer.After the transistor saturation,the feedback signal falls the capacitor discharges,and the oscillation starts again .
5)On circuits. 6)Push-pull:designer arranges the biasing of push-pull amplifier to set the Q point at cutoff;RS flip-flop:designed, that circuit can set the Q point to high or reset it to low;Blocking ocillator:Unlike a multivibrator,the output of this circuit is sharp pulses with brad pauses between them.It has also a transformer;Multivibrator:is a rectangle pulse generator with the positive feedback.
7)Advantages:simple principle of operation, low price , high reliability.Disadvantages:unstable and temperature dependent.Output waveform has distortions and changes with time.
8)Monostables:It generates the only pulse after switching on, and on continue operation, an input signal must enter the circuit.The pulse width of the single-short output signal is determined by R and C values.At the initial state, the transistor T2 passes the current and T1 is closed.The capacitor is charged.After Uin enters T1,the T1switches on and the capacitor closes T2.The capacitor discharges through R and not T1 but T2 continues conducting thanks to the base current from R1.After the full discharging of the capacitor,T2 switches on again and T1 switches off.
In case of the negative feedback, the midband becomes: larger narrow no matter no band
How many valence electrons a silicon atom has? 1 2 4 8
Ticket No14
U1
U2
NOT U1
U1 OR U2
U1 NOR U2
U1 AND U2
U1 NAND U2
0
0
1
0
1
0
1
0
1
1
1
0
0
1
1
0
0
1
0
0
1
1
1
0
1
0
1
0
Mark the inputs and outputs, each element, and all signals of the circuits.

Fill in the truth table.

Draw the circuit diagrams of the devices that implement the columns of the table.

What each device is called?

Draw the schematic symbol of each device.

Draw the input and output signals of these five devices.

Are there analog, switching, or digital devices? They are build on the digital gates- dig. Devices. You can make switching devices of them

Inscribe the logical equation that each circuit solves. OR+,AND*,NOT-,

Draw other circuits of such kind and describe their elements and performance .

Round the true answers

How many electrons are there in the valence orbit of a germanium atom within a crystal? 8

The base of a bipolar transistor is made of: semiconductor
Ticket No15
diode
thyristor

The Main Problem

Mark the inputs, outputs, and each element of the circuit.

What device this circuit diagram belongs to? Forward biased diode circuit

Plot the voltage and current waveforms of this device.

Inscribe the axes and mark the specific regions and points of the characteristics.

What are the typical values of the quantities in the points, which you have marked?

Tell about the powers, voltages, and currents of the device. It is a nonlinear device meaning that its output current is not proportional to the voltage. Easy direction of electron flow is against the diode arrow. Its typical bulk resistance is less than 1 oom and forward voltage drop between 0.7 and 2 V. Due to high reverese resistance, a diode has a low leakage current. At breakdown, the diode goes into avalvance that may destroy it. The current is small for the first few tenths of a volt. Above knee voltage, the slightest increase in diode voltage produces a large growth in current. If the current is too large, approaching to the burnout current, the excessive heat will destroy the device. Closely related to the max forward current and forward voltage drop is the maximum power dissipation that indicates how much power the diode can safely dissipate without shortening its life.

Plot the same waveforms for the circuit built on the thyristor instead of the diode.

List the advantages and disadvantages of these devices.

• Easy to destroy the device by too high voltage, current or frequency values
  
• Large currents cause significant voltage drops
  
• It can convert alternating current/voltage into direct one
  
• Can be applied in detectors, which fin signal in noisy condtitions
  
• Used as a switch also, ideal rectifier acts like a switch that closes the current flow when foward biased and opens it when reverese biased
  

Round the true answers

What is resistance of metal due to? voltage current ionization vibration

What are the majority carriers in the base of an npn transistor?
electrons holes protons neurons