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8/12/2019 Electronics Basis1

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Kirchhoff's voltage law (KVL)

The sum of voltage drops at a current loop is zero.

Vk = 0

Kirchhoff's Current Law (KCL)

This is Kirchhoff's first law.

The sum of all currents that enter an electrical circuit junction is 0. When

the currents enter the junction have positive sign and the current that leave

the junction have negative sign:

Another way to look at this law is that the sum of currents that enter a

junction is equal to the sum of currents that leave the junction:

KCL example

I1 and I2 enter the junction

I3 leave the junction

I1=2A, I2=3A, I3=-1A, I4= ?

Solution:

Ik = I1+I2+I3+I4 = 0

I4 = -I1 - I2 - I3 = -2A - 3A - (-1A) = -4A

Since I4 is negative, it leaves the junction.

Kirchhoff's Voltage Law (KVL)

This is Kirchhoff's second law.


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The sum of all voltages or potential differences in an electrical circuit loop

is 0.

KVL example

VS = 12V, VR1 = -4V, VR2 = -3V

VR3 = ?

Solution:

Vk = VS + VR1 + VR2 + VR3 = 0VR3 = -VS - VR1 - VR2 = -12V+4V+3V = -5V

The voltage sign (+/-) is the direction of the potential difference.

Ohm's Law

Ohm's law defines a linear relationship between the voltage and the

current in an electrical circuit.

Ohm's law definition

The resistor's current I in amps (A) is equal to the resistor's voltage VR=V

in volts (V) divided by the resistance R in ohms ():

V is the voltage drop of the resistor, measured in Volts (V). In some cases

Ohm's law uses the letter E to represent voltage. E denotes electromotive

force.


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I is the electrical current flowing through the resistor, measured in

Amperes (A)

R is the resistance of the resistor, measured in Ohms ()

Voltage calculation

When we know the current and resistance, we can calculate the voltage.

The voltage V in volts (V) is equal to the to the current I in amps (A) times

the resistance R in ohms ():

V=I\times R

Resistance calculation

When we know the voltage and the current, we can calculate the resistance.

The resistance R in ohms () is equal to the voltage V in volts (V) dividedby the current I in amps (A):

R=\frac{V}{I}

Since the current is set by the values of the voltage and resistance, the

Ohm's law formula can show that:

If we increase the voltage, the current will increase.

If we increase the resistance, the current will reduce.

Example #1


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Find the current of an electrical circuit that has resistance of 50 Ohms and

voltage supply of 5 Volts.

Solution:

V = 5V

R = 50

I = V / R = 5V / 50 = 0.1A = 100mA

Electrical Voltage

Electrical voltage is defined as electric potential difference between two

points of an electric field.

Using water pipe analogy, we can visualize the voltage as height difference

that makes the water flow down.

V = 2 - 1

V is the voltage between point 2 and 1 in volts (V).

2 is the electric potential at point #2 in volts (V).

1 is the electric potential at point #1 in volts (V).

Voltage drop

Voltage drop is the drop of electrical potential or potential difference on the

load in an electrical circuit.

Voltage Measurement

Electrical voltage is measured with Voltmeter. The Voltmeter is connectedin parallel to the measured component or circuit.

The voltmeter has very high resistance, so it almost does not affect the

measured circuit.


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Resistor:

Resistor reduces the current flow.

Resistor is an electrical component that reduces the electric current.

The resistor's ability to reduce the current is called resistance and is

measured in units of ohms (symbol: ).

If we make an analogy to water flow through pipes, the resistor is a thin

pipe that reduces the water flow.

Material Carbon or metal(This is made by wrapping a carbon track

around a ceramic core)

Capacitor:

Capacitor is used to store electric charge. It acts as short circuit with AC

and open circuit with DC.

Inductor

Inductor is an electrical component that stores energy in magnetic field.

The inductor is made of a coil of conducting wire.

In an electrical circuit schematics, the inductor marked with the letter L.

The inductance is measured in units of Henry [L].

Inductor reduce current in AC circuits and short circuit in DC circuits.

Thermistor:

Thermal resistor - change resistance when temperature changes

Photo resistor/LDR:

Photo-resistor - change resistance with light intensity change


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Voltmeter Measures voltage. Has very high resistance. Connected in parallel.

Ammeter Measures electric current. Has near zero resistance. Connected serially.

Ohmmeter Measures resistance

Wattmeter Measures electric power
http://en.wikipedia.org/wiki/Voltmeterhttp://en.wikipedia.org/wiki/Ammeterhttp://en.wikipedia.org/wiki/Ohmmeterhttp://en.wikipedia.org/wiki/Wattmeterhttp://en.wikipedia.org/wiki/Wattmeterhttp://en.wikipedia.org/wiki/Ohmmeterhttp://en.wikipedia.org/wiki/Ammeterhttp://en.wikipedia.org/wiki/Voltmeter


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Electrical & Electronic Circuit Laws

Electrical and electronic circuit laws, define the operation of the circuits.

Coulomb's law

DC circuit laws

Kirchhoff's laws (KVL / KCL)

Ohm's law

Voltage divider rule

Coulomb's lawcalculates the electric force F in newtons (N) between two

electric charges q1 and q2 in coulombs (C)

with a distance of r in meters (m):


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Resistor color code

The resistance of the resistor and its tolerance are marked on the resistor

with color code bands that denotes the resistance value.

There are 3 types of color codes:

4 bands: digit, digit , multiplier, tolerance.

5 bands: digit, digit, digit , multiplier, tolerance.

6 bands: digit, digit, digit , multiplier, tolerance, temperature coefficient.

Units prefix table

Prefix Symbol factor Example

pico p 10-12 1pF = 10-12F

nano n 10-9 1nF = 10-9F

micro 10-6 1A = 10-6A

milli m 10-3 1mA = 10-3A

kilo k 10 3 1k = 1000

mega M 10 6 1MHz = 106Hz

giga G 10 9 1GHz = 109Hz


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Diode SymbolsDiode schematic symbols of electronic circuit - Diode, LED, Zener diode, Schottky diode,

photodiode, ...

Symbol Name Description

DiodeDiode allows current flow in one

direction only (left to right).

Zener Diode

Allows current flow in one direction,

but also can flow in the reverse

direction when above breakdown

voltage

Schottky DiodeSchottky diode is a diode with low

voltage drop

Varactor / Varicap Diode Variable capacitance diode

Tunnel Diode

Light Emitting Diode (LED)LED emits light when current flows

through

Photodiode

Photodiode allows current flow when

exposed to light

Passive components

Passive components do not need additional power source to operate and

can not have gain.

Passive components include: wires, switches, resistors, capacitors,

inductors, lamps, ...

Active components

Active components need additional power source to operate and can have

gain.Active components include: transistors, relays, power sources,

amplifiers, ...


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Digital electronics:

Flip flop:

- Flip-flops, also called bistable gates

- it is the basic element of storage and store the binary bit(0 or 1)

- By sending a signal to the flip-flop, the state can be changed

Types:

S-R (set/reset)

T (toggle)

D (delay).

J-K (possibly named for Jack Kilby) and

SR Flip Flop:

Truth Table


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OPERATION

S.N. Condition Operation

1 S = R = 0 : No change

If S = R = 0 then output of NAND gates 3 and 4 are forced to become 1.

Hence R' and S' both will be equal to 1. Since S' and R' are the input ofthe basic S-R latch using NAND gates, there will be no change in thestate of outputs.

2 S = 0, R = 1, E = 1Since S = 0, output of NAND-3 i.e. R' = 1 and E = 1 the output of NAND-4 i.e. S' = 0.

Hence Qn+1= 0 and Qn+1bar = 1. This is reset condition.

3 S = 1, R = 0, E = 1Output of NAND-3 i.e. R' = 0 and output of NAND-4 i.e. S' = 1.

Hence output of S-R NAND latch is Qn+1= 1 and Qn+1bar = 0. This isthe reset condition.

4 S = 1, R = 1, E = 1As S = 1, R = 1 and E = 1, the output of NAND gates 3 and 4 both are 0i.e. S' = R' = 0.

Hence the Racecondition will occur in the basic NAND latch.

4. s=1,r=1 means output q& q = 1. So this is indeterminate, bcz Flip

flop outputs is compulsory complement

D flip flop:


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Truth table

Operation


1 E = 0 Latch is disabled. Hence is no change in output.

2 E = 1 and D = 0

If E = 1 and D = 0 then S = 0 and R = 1. Hence irrespective of the present

state, the next state is Qn+1= 0 and Qn+1bar = 1. This is the reset condition.

3 E = 1 and D = 1if E = 1 and D = 1, then S = 1 and R = 0. This will set the latch and Q n+1= 1

and Qn+1bar = 0 irrespective of the present state.

T-flip flop:


1 T = 0, J = K = 0 The output Q and Q bar won't change


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2 T = 1 ,J = K = 1 output will toggle corresponding to every leading edge of clock signal.

JK flip flop

Truth table:


1 J = K = 0 (No change)When clock = 0, the slave becomes active and master is inactive. Butsince the S and R inputs have not changed, the slave outputs will alsoremain unchanged. Therefore outputs will not change if J = K =0.

2 J = 0 and K = 1 (Reset)

Clock = 1: Master active, slave inactive. Therefore outputs of the

master become Q1= 0 and Q1bar = 1. That means S = 0 and R =1.

Clock = 0: Slave active, master inactive Therefore outputs of the slavebecome Q = 0 and Q bar = 1.

Again clock = 1: Master active, slave inactive. Therefore even with thechanged outputs Q = 0 and Q bar = 1 fed back to master, its outputswill Q1 = 0 and Q1 bar = 1. That means S = 0 and R = 1.

Hence with clock = 0 and slave becoming active the outputs of slave


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will remain Q = 0 and Q bar = 1. Thus we get a stable output from theMaster slave.

3 J = 1 and K = 0 (Set)

Clock = 1: Master active, slave inactive. Therefore outputs of the

master become Q1= 1 and Q1bar = 0. That means S = 1 and R =0.

Clock = 0: Slave active, master inactive Therefore outputs of the slavebecome Q = 1 and Q bar = 0.

Again clock = 1: then it can be shown that the outputs of the slave arestabilized to Q = 1 and Q bar = 0.

4 J = K = 1 (Toggle)

Clock = 1: Master active, slave inactive. Outputs of master will toggle.So S and R also will be inverted.

Clock = 0: Slave active, master inactive. Outputs of slave will toggle.

These changed output are returned back to the master inputs. Butsince clock = 0, the master is still inactive. So it does not respond tothese changed outputs. This avoids the multiple toggling which leads tothe race around condition. The master slave flip flop will avoid the racearound condition.

SR and JK Flip flop difference indeterminate.

D & T flip flops are Negative edge Triggered flip flop.

JK flip flop is Positive edge Triggered flip flop.

Flip flop Clock pulse positive edge is 0 to 1

Flip flop Clock pulse Negative edge is 1 to 0


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Shift register

The binary data in a register can be moved within the register from one

flip-flop to another. The registers that allow such data transfers are called

as shift registers. There are four mode of opearation of a shift register.

Serial Input Serial Output

Serial Input Parallel Output

Parallel Input Serial Output

Parallel Input Parallel Output

Counter

Counter is a sequential circuit. A digital circuit which is used for a countingpulses is known counter. Counter is the widest application of flip-flops. Itis a group of flip-flops with a clock signal applied. Counters are of twotypes.

Asynchronous or ripple counters

Synchronous counters.

Application of the counters

Frequency counters

Digital clock

Time measurement

A to D converter

Frequency divider circuits

Digital triangular wave generator


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SignalSignalcan be defined as a physical quantity, which contains some information. It is a function of one or more thanone independent variables. Signal are of two types.

Analog Signal

Digital Signal

Analog SignalAn analog signal is defined as the signal having continuous values. Analog signal can have infinite number ofdifferent values. In real world sceanario, most of the things observed in nature are analog. Examples of the analogsignals are following.

Temperature

Pressure

Distance

Sound

Voltage

Current

Power

Graphical representation of Analog Signal(Temperature)

The circuits that process the analog signals are called as analog circuits or system. Examples of the analog systemare following.

Filter


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Amplifiers

Television receiver

motor speed controller

DISADVANTAGE OF THE ANALOG SYSTEMS

Less accuracy

Less versatslity

More noise effect

More distortion

More effect of weather

Digital SignalA digital signal is defined as the signal which has only a finite number of distinct values. Digital signal are notcontinuous signal. In the digital electronic calculator, the input is given with the help of switches. This input isconverted into electrical signal which having two discrete values or levels. One of these may be called low level andanother is called high level. The signal will always be one of the two levels. This type of signal is called digital signal.Examples of the digital signal are following.

Binary Signal

Octal Signal

Hexadecimal Signal

Graphical representation of the Digital Signal (Binary)

The circuit that process that digital signal are called digital system or digital circuit. Examples of the digital system arefollowing.

Registers


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Flip-flop

Counters

Microprocessors

Logic GatesLogic gates are the basic building blocks of any digital system. It is an electronic circuit having one or more than oneinput and only one output. The relationship between the input and the output is based on a certain logic. Based onthis logic gates are named as AND gate, OR gate, NOT gate etc.

Combinational CircuitsCombinational circuit is circuit in which we combine the different gates in the circuit for example encoder, decoder,multiplexer and demultiplexer. Some of the characteristics of combinational circuits are following.

The output of combinational circuit at any instant of time, depends only on the levels present at input terminals.

The combinational circuit do not use any memory. The previous state of input does not have any effect on the presentstate of the circuit.

A combinational circuit can have a n number of inputs and m number of outputs.

BLOCK DIAGRAM

DecoderA decoder is a combinational circuit. It has n input and to a maximum m = 2n outputs. Decoder is identical to ademultiplexer without any data input. It performs operation which are exactly opposite to those of an encoder.

BLOCK DIAGRAM


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Examples of Decoders are following.

Code converters

BCD to seven segment decoders

Nixie tube decoders

Relay actuator

EncoderEncoder is a combinational circuit which is designed to perform the inverse operation of the decoder. An encoder hasn number of input lines and m number of output lines. An encoder produces an m bit binary code corresponding tothe digital input number. The encoder accepts an n input digital word and converts it into an m bit another digitalword.

BLOCK DIAGRAM

Examples of Encoders are following.

Priority encoders

Decimal to BCD encoder

Octal to binary encoder

Hexadecimal to binary encoder

Sequential CircuitsThe combinational circuit do not use any memory. Hence the previous state of input does not have any effect on thepresent state of the circuit. But sequential circuit has memory so output can vary based on input. This type of circuitsuse previous input , output ,clock and a memory element.


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BLOCK DIAGRAM


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