Resistance is proportional to the length and inversely proportional to the cross sectional area of the material

Where, is defined as resistivity, in Ohm-meter ( ), which is simply the resistance per unit length times cross-sectional area.

X X

R

A

lR

Symbol of a resistor

m

1R 4R3R2R

X

Y

1R3R

4R2R

(a)(b)

X

Y

Resistances connected in series and parallel are calculated using the following formula.

Series connection Parallel connection

nserieseq RRRRR ................321_

nparalleleq RRRRR

1...................

1111

321_

L

X Y

i

NkL

Purpose-made conductor coils are called inductors. When current flows electromagnetic field is established. The electromagnetic lines of force surrounds the conductor and the magnetic lines of force becomes concentrated. When the current changes, the electromagnetic field changes accordingly and the changing electromagnetic field causes an induced voltage in a direction in opposite to the flow of current. This property is referred to as inductance.

l

N turns

A

l

N turns

A

Symbol

Surface-1

Surface-2

Electrode-1

Electrode-2

Dielectric material

C

X

Y

dC r

0

A capacitor is an energy storage passive component. The term capacity signifies "what is the capacity of the surfaces in holding the electrical charges." It stores charge and hence electric field energy. The equivalent capacitance of a series combination is always less than any individual capacitance in the combination and can be expressed using the following equation. On the other hand, the parallel connection adds up all the individual capacitances

Inductance

Inductive reactance

Frequency

Inductive reactance

(a)

Capacitance Frequency

Capacitive reactance Capacitive reactance

(b)

Inductive reactance versus inductance and frequency curve.

Capacitive reactance versus capacitance and frequency curve.

p-type Semiconductor material

Immobile Acceptor atoms (Trivalent)

A piece of intrinsic Semiconductor material

n-type Semiconductor material

Immobile Donor atoms (Pentavalent)

__

__

_

__

__

_

_

____

_

(a)

(b)

(c)

Terminal Terminal

Terminal Terminal

Terminal Terminal

_

_

Flow of current

Flow of electrons

Flow of current

Flow of holes

A

A

A

B

B

B

Flow of current

Flow of electrons

_

If the donors are added, the intrinsic semicond-uctor becomes n-type semiconductor and if the acceptors are added it becomes p-type semicon-ductor. n-type semico-nductor materials have loosely-attached free-electrons and p-type semiconductor materials have loosely-attached free-holes. The electrons and holes, in the respective extrinsic semi conductors, are called charge carriers

p-type n-type +

+

+

-

-

-

Majority carriers (holes)

_

_

__

_ _

_

_

_

_

_

Majority carriers (electrons)

Depletion layer

Uncovered immobile atomsUncovered immobile atoms

Potential barrier

Electrode Electrode

n-typep-type

(a)

(b)

Semiconductor diodes or junction diodes are two terminal electronic devices made up of two types of semiconductor materials. One side of the device has n-type material and the other side has p-type.

A depletion layer is a layer in which the charge carriers are absent

+ -

Voltage source

Forward-biased p-n junction diode

+ -

Voltage source

Reverse-biased p-n junction diode

(a) (b)

Voltage in volts

Current is mA

TV

Current is mA

Voltage in volts

0IbV

The behavior of a junction diode is such that it offers a low resistance to electric current in one direction and a high resistance to it in the reverse direction. This property is a requirement in the context of signal manipulation and processing. The current equation in the diode is given above.

)1(0 kT

qV

eII

I is the diode current, q is charge of the carriers, k is a constant, V is the applied voltageT is temp. in degrees K

Reverse voltage

Capacitance

Diode voltage

Current

Negative coefficient of

resistance

Varacter Tunnel

Varactor exploits the depletion layer in terms of a parallel plate capacitor, whose capacitance is controlled by applying reverse voltage. The capacitance across the junction is inversely proportional to the width of the depletion layer. The varactors useful for designing VCO, FM modulators and demodulators and tuning circuits.

In the tunnel diode, the current through the device decreases as the voltage increases within a certain range This property, known as negative resistance, makes it useful as a switch and oscillators.

input Output +

-

+

-

Diode

Common terminal called GROUND

(Common to both input and Output)

Amplitude

Time

Amplitude

Time

Amplitude

Time

Amplitude

Time

(b)

(a)

(c)

(d)(a)

In general, junction diodes are referred to as rectifiers because when an alternating signal (voltage or current) say a sinusoidal or rectangular signal is applied (assuming ideal diode) the output would be a signal containing only positive half-cycles.

P N P N P N

Collector (C) Collector (C)Emitter (E) Emitter (E)

Base (B)Base (B)

B

C

E

input

Output

Common-collector configuration

B

E C

OutputInput

Common-base configuration

n-p-n

n-p-n

B

C

Einput

Output

Common-emitter configuration

n-p-n

(a) (b)

(f)

C

Bn-p-n (Symbol)

E

(c)

C

B

E

p-n-p (Symbol)

(d)

(e) (g)

(e) The common emitter configuration of an n-p-n transistor(f) the common collector configuration of an n-p-n transistor(g) The common base configuration of an n-p-n transistors

(a) A pnp transistor(b) An npn transistor

(c) Symbol of a pnp(d) Symbol of npn

CEV

123 BBB III

3BI

2BI

1BI

(a)

In mA

In volts

in mA

in mA

in mA

CI

SAT

UR

AT

ION

RE

GIO

N

Cut- Off Region

CEV(b)

In mA

In volts

CI

ACTIVE REGION

The output characteristics of a typical transistor is shown. The shadow portion of the figure provides much information about the transistor. The entire quadrant is divided into three regions, the active region, the saturation region, and the cut-off region. Each point in the quadrant is called an operating point or Q-point of the transistor.

Emitter current Collector current

Base current

BE C

EJ CJ

%2

%100

%98

The collector current is the sum of the emitter current and the base current.

BEC III

B

C

E

input

Output

Common-emitter configuration

n-p-n

+Vcc

Ground

+

_

+

_BEV

CEV

1R

2R

LR

ER

cC

EC

bCiR

ccV iR- Biasing voltage (source)

CEV - Collector to Emitter voltage

BEV - Base to Emitter voltage

- Resistance at input circuit

- Biasing resistances

- Load resistance

1R 2R

LR

ER - Feedback resistance bC- Blocking capacitor (it block dc component)

cC - Coupling capacitor (to next stage)EC -Feedback capacitor

The characteristic of a transistor is such that a small voltage change in the base-emitter junction will produce large current change in the collector and emitter, whereas small changes in the collector-emitter voltage have little effect on the base. A typical transistorized amplifying circuit is given.

DI

DI

DSV

Drain (D)

Source (S)

(Gate (G)

GSV_

+

_

+

n-type

P-t

ype

n-channel

P-type

Depletion layerD

eple

tion

la

yer

Bipolar junction transistors have low input impedance small high-frequency gain, and are to some extend non-linear. However, high input impedance is desirable for low power consumption. FET overcomes this problem.

Junction Field Effect Transistor (JFET) or simply FET are of two types, p-channel FET and n-channel FET. In each case, a semiconductor bar called channel of one type of semiconductor material is located inside a bulk of material of the other kind.

p

n

Base-1

Base-2

Emitter+

-

+

-

(a) Ground

1EBV12BB

V

2B

1B

E

(b)

1R

2R

AA

Equivalent circuit

pV

+

-

1B

2B2B

1B

UJT Symbol

(c)

E

(d)

Characteristics

Emitter current

1EBV

pV

Equivalent diode

Cathode

Anode

A typical construction of a transistor defines itself as a unijunction transistor (UJT), a transistor with only one junction and three terminals. UJT exhibits a negative resistance characteristic as can be seen from the V-I plot This switching feature can be exploited in designing oscillators.

p

n

p

n

Anode

Cathode

Gate

+

- DV

GV

SCR Symbol

+

-

Anode

Cathode

Ground

Gate

(a) (b) (c) Characteristics

SCR current

Gate voltage

Forward breakover voltage

Forward conduction

Reverse breakdown voltage

J1

J2

J3

SCR stands for Silicon Controlled Rectifier. SCRs are four-layered diodes and shows negative resistance characteristics. It has three junctions and three terminals. The application of a forward voltage is not enough for conduction since the junction is reverse biased. A gate signal can control the conduction of the rectifier.

DV 2J

+

_Inverting terminal

Noninverting terminal

Positive supply

Negative supply

Output

Input signal can either be connecter to inverting or noninverting terminal

Operational Amplifiers (OPAMP) are analog ICs and are basically amplifiers, but can be configured in a variety of ways in order to design low- and high-pass filters, differential amplifiers, oscillators, impedance matching circuits (unit follower), sample and hold (S/H) circuits, current limiters, rectifiers, instrumentation amplifiers, comparators, zero crossing detectors, and so on.

-

+inV+

-

oV+

-

-

+inV+

-

oV+

-

1R

fR

1R

Open-loop(Closed-loop)

(a) (b)

The gain of the OPAMP is defined as the ratio of output voltage to the input voltage. Two different types of gains are encountered in the OPAMP: open-loop gain and closed loop gain. Open-loop gains again are of two types, open-loop differential mode gain and open-loop common mode gain