Contents

Diodes. 2

Diodes(Number and Coding schemes) 2

PIV(Peak Inverse Voltage) 2

Parameters of a Diode. 3

Zener Diodes. 3

BJT. 4

Saturation. 4

DC-Biasing. 4

DC-Load Line. 5

re model 6

Hybrid Model 6

Single stage amplifiers. 7

CE amplifiers. 8

CC amplifiers. 9

CB amplifier. 10

Effect of Source & Load Resistance. 10

 Model (Giacoletto) 11

Summary of Single Stage BJT Amplifiers. 12

Effect of Source & Load Resistance. 12

Frequency Response of BJT Amplifiers. 13

JFET (Junction Field Effect Transistor) 14

DC-Biasing. 14

gm Model 15

Single stage amplifiers without source and load resistance. 15

Summary of Single Stage BJT Amplifiers. 16

Abstract Amplifier Model 17

MOSFET. 18

Symbol 18

MOSFET V-I Relation. 19

MOSFET Common Circuits. 20

MOSFET Inverters. 21

CS Fixed Bias Amplifier. 22

Channel Width Modulation. 23

Effect of substrate voltage. 24

Effect of temperature. 24

Breakdown in Mosfet 24

Capacitances in Mosfet 24

Examples. 25

OP-AMP. 26

Op-Amp Basics-I 26

Basic OP-Amp Circuits. 27

FEEDBACK Circuits. 28

The Feedback Factor. 29

Types of Feedback. 29

Examples of Feedback. 29

 

 

 

Diodes

 

 

Diodes(Number and Coding schemes)

 

There are a number of common, standard and manufacturer-driven numbering and coding schemes for diodes; the two most common being the EIA/JEDEC standard and the European Pro Electron standard

 

EIA/JEDEC

A standardized 1N-series numbering system was introduced in the US by EIA/JEDEC (Joint Electron Device Engineering Council) about 1960. Among the most popular in this series were: 1N34A/1N270 (Germanium signal), 1N914/1N4148 (Silicon signal), 1N4001-1N4007 (Silicon 1A power rectifier) and 1N54xx (Silicon 3A power rectifier)

 

Pro Electron

The European Pro Electron coding system for active components was introduced in 1966 and comprises two letters followed by the part code. The first letter represents the semiconductor material used for the component (A = Germanium and B = Silicon) and the second letter represents the general function of the part (for diodes: A = low-power/signal, B = Variable capacitance, X = Multiplier, Y = Rectifier and Z = Voltage reference), for example:

 

·         AA-series germanium low-power/signal diodes (e.g.: AA119)

·         BA-series silicon low-power/signal diodes (e.g.: BAT18 Silicon RF Switching Diode)

·         BY-series silicon rectifier diodes (e.g.: BY127 1250V, 1A rectifier diode)

·         BZ-series silicon Zener diodes (e.g.: BZY88C4V7 4.7V Zener diode)

 

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/ \ \ \ variant (A,B,C for transistors implies low, medium or high gain)
/ \ \____ serial number (3 digits or letter and 2 digits)
/ \_____ device type:
AGermanium ASignal Diode
B5ilicon C=LF Low Power transistor
CGaAs DPower transistor
FRF transistor (or FET)
PPhotosensitive transistor
TTriac or Thyristor
YRectifier Diode
Z=Zener diode

 

PIV(Peak Inverse Voltage)

 

 

·         PIV is the maximum voltage that a reverse biased can withstand without going into avalanche breakdown

 

Type of rectifier

Peak Inverse Voltage

Diagram

Half wave rectifier

 

Full wave rectifier

 

CT Full waver rectifier

 


 is the peak of the input sinusoidal.

 

Parameters of a Diode

 

 

Saturation current

Emission coefficient

Series resistance

Junction capacitance

Transit time

Reverse bias breakdown voltage

Reverse bias breakdown current

 

 

Zener Diodes

 

Zener Diode  V- I Characteristics

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ON and OFF states of Zener Diode

 

 

 

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The Zener potential is

 

What is the minimum and maximum value of to turn ON the Zener diode and to ensure that it does not exceed its maximum current.

What is the minimum and maximum value of  that will keep the Zener diode ON and also prevent it from exceeding its maximum current.

 

BJT

Saturation

 

The voltage  gives the actual status of the transistor in terms of saturation and active mode.

 

Type

Status

NPN

Negative

Active

PNP

Positive

Active

 

Type

Status

NPN

Positive

Saturation

PNP

Negative

Saturation

 

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A transistor in saturation cannot amplify signals faithfully. Proper amplification takes place when transistor is in active mode.

 

DC-Biasing

 

Fixed Bias

 

 

Emitter

Bias

 

 

 

Voltage

Divider

Bias

 

 

 

 

 

 

Collector

Feedback Bias

 

 

Emitter Follower Bias

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DC-Load Line

 

re model

 

 

 npn Common base

 

 

npn Common emitter

 

β r_e

 

 

 

 

Hybrid Model

 

 

 

  

Hybrid Model

Comparison with  Model

Common Base

 

 Parameters

 Parameters

0

Common Emitter

 

 

 Parameters

 Parameters

0

1/hoe

Complete hybrid parameter with source and load resistance

 

 

 

 

 

 

Single stage amplifiers

 

Common emitter

Fixed Bias

 

Common Emitter

Collector Feedback Bias

Common emitter

Self Bias (unbypassed emitter)

Common Emitter

Collector Feedback Bias (unbypassed emitter)

 

Common emitter

Self Bias (bypassed emitter)

 

 

Common Emitter

Collector Feedback Bias (bypassed emitter)

 

Common emitter

Voltage Divider Bias (bypassed emitter)

 

 

 

Common emitter

Voltage Divider Bias (unbypassed emitter)

 

 

Common collector

Self Bias

 

 

Common base

Fixed Bias

 

·        

The results for  and  change if  is taken into account.

 

CE amplifiers

 

 

 

 Calculation without

(Ignoring the effect of  and )

Calculation with

(Ignoring the effect of  and )

 

CC amplifiers

 

 

 

 

 

 Calculation without

(Ignoring the effect of  and )

Calculation with

(Ignoring the effect of  and )

 

 

 

CB amplifier

 

 

 

 

 Calculation without

(Ignoring the effect of  and )

Calculation with

(Ignoring the effect of  and )

 

 

 

 

 

 

 

Effect of Source & Load Resistance

 

Let us assume that a transistor has the following small signal parameters:

 

Voltage Gain

Current Gain

Input Impedance

Output Impedance

 

These parameters are used to model a two port network from which the effect of source and load resistance is found out.

 

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Effect of source resistance  on gain

Effect of source resistance  on gain

Effect of source resistance  on gain

 

 Model (Giacoletto)

 

·         Also known as Giacoletto model

·         Complete model for low and high frequencies.

·         At low frequencies  and  models are used for calculation simplicity.

 

 

Base contact

+ Base bulk + Base spreading resistance

 

usual input resistance of CE

very high in

(10-40)

transconductance

 

 

*u subscript stands for union between base and collector.

 

Summary of Single Stage BJT Amplifiers

 

 

Common Emitter Self Bias Voltage Divider

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Common Emitter Collector Feedback

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Common Collector (Emitter Follower)

 

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Common Base

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Effect of Source & Load Resistance

 

 

 

 

 

 

Frequency Response of BJT Amplifiers

Low Frequency Cut-offs

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High Frequency Cut-offs

 

 

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There are two capacitances  which cause high frequency gain roll-off. They are wiring capacitance and inter-electrode capacitance.

 

Wiring capacitance :  

Inter-electrode capacitance :

 

 

 is split into input and output side capacitance using Miller's Theorem.

 

 

 

The change in current gain with frequency is also responsible for high frequency gain roll-off. This cut off is given by

 

 

Relation between gain bandwidth  product and

 

·        

 

JFET (Junction Field Effect Transistor)

 

DC-Biasing

 

Fixed Bias

 

 

 

Self-Bias

 

Voltage Divider Bias

 

 

 

 

Depletion Type Voltage Divider Bias

 

 

 

Enhancement Type Voltage Divider Bias

 

 


Enhancement Type Drain Feedback Bias

 

 

 

gm Model

 

 

 

 

 

Transconductance

Channel conductance

MOSFET

 

 

 

JFET


, called the device parameter =

 

Single stage amplifiers without source and load resistance

 

 

Common source

Fixed Bias

 

 

 

Common source

Drain Feedback

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Common source

Self-Bias with unbypassed

 

 

Common source

Voltage Divider with bypassed

 

 

Common drain (Source Follower)



 

Common gate


 

 

Summary of Single Stage BJT Amplifiers

 

 

Common Source

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Common Source

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Common Drain

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Common Gate

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Abstract Amplifier Model

 

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Input Impedance

Output Impedance

Current Gain

Voltage Gain

 

 

Overall Gain

 

 

MOSFET

 

Symbol

 

Depletion Type

Enhancement Type

n-MOS

 

 

 

 is positive. Positive  increases the drain current whereas negative  decreases it. This is an ON device by default.

 

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 is positive. This is an OFF device by default.  turns the device ON.

 

 

p-MOS

 

 

 

 is negative. Negative  increases the drain current whereas positive  decreases it. This is an ON device by default.

 

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 is negative. This is an OFF device by default.  turns the device ON.

 

 

MOSFET V-I Relation

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Conditions necessary for saturation:

 

Current in linear (triode) region

Current in saturation

Process transconductance parameter

 is capacitance per unit area

Transconductance

Resistance

 

MOSFET Common Circuits

 

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The mosfet in this schematic is always in saturation

 

 

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The maximum value of  that will keep Q2 in saturation is

 

 

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Both the mosfets are identical

 

The minimum voltage source  must provide to ensure that both mosfets are in saturation is

 

 

 

 

MOSFET Inverters

N-MOSFET Enhancement Type

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Input

Output

 

N-mosfet enhancement type TURNS-ON when gate voltage is greater than , the threshold voltage.

 

 is positive for n-mosfet enhancement type

P-MOSFET Enhancement Type

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Input

Output

 

P-mosfet enhancement type TURNS-ON when gate voltage is lesser than , the threshold voltage.

 

 is negative for p-mosfet enhancement type

N-MOSFET Enhancement Type (Driver-Load) Inverter

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Load is always ON operating in saturation because gate is tied to the drain.

 

When  is 0V  because Driver is OFF

When   because Driver is ON

 

In this arrangement power consumption is more than CMOS inverter because Load is always ON .

 

Note that in CMOS inverter drains are tied together whereas here drain and source are tied together.

CMOS Inverter

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Load is a P-mosfet enhancement type device while Driver is an N-mosfet enhancement type.

 

When  Driver is OFF but Load is ON because



 

When  Driver is ON but Load is OFF because



 

Input

Output

 

It is not necessary that threshold voltage of the Driver and the Load be same

 

CS Fixed Bias Amplifier

 

 

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Channel Width Modulation

 

 

No channel width modulation

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Effect on current due to channel width modulation and introduction of process parameter

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Early voltage and determination of

 

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Finite output resistance due to channel width modulation

 

 

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Effect of substrate voltage

 

 

The effect of body effect is that the threshold voltage is reduced

 

 

 and  are process parameters and  is the  when  is zero.

 

In an n-MOS device the substrate is connected to the most negative voltage in the system so as to keep  negative.

 

Effect of temperature

 

Drain current decreases with increase in temperature unlike BJT

 

Breakdown in Mosfet

 

There are three kinds of breakdown in mosfet

 

1.      Breakdown of drain and substrate region due to high drain voltage. This is avalanche breakdown

 

2.      If the channel width is small the depletion region at drain may cross the channel and overlap with the region at source. This causes increase in the drain current. This is called punch-through.

 

3.      Breakdown of gate-oxide if static charge is deposited at the gate. This causes permanent damage.

 

Capacitances in Mosfet

 

 

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Triode Region

 

 

Saturation Region

 

 

Cut off

 

 

Unity gain bandwidth frequency

 

Upper cut off frequency

 

 

 

Examples

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OP-AMP

 

 

 

 

 

Assuming  simplifies the above

 

 

 

Op-Amp Basics-I

 

 

Common-mode Rejection Ratio

 


 

Input Offset- Voltage

 

 

 

 

 

Effect on output voltage due to input offset voltage

 

 

 

Input Offset- Current

Effect on output voltage due to input offset current

Input Bias- Current

Relationship between Input bias current and Input offset current

Slew Rate

 

 

 

Cut off frequency

Relation between open loop gain, gain-bandwidth frequency and the cut-off frequency

 

Basic OP-Amp Circuits

 

Inverting amplifier

 

Non-inverting amplifier

 

Subtract

 

Summing Amplifier

 

Integrator

 

Differentiator

 

Instrumentation Amplifier

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FEEDBACK Circuits

 

 

 

 

The Feedback Factor

 

Feedback factor =

 

Overall gain with feedback

 

Types of Feedback

 

Type of feedback

Input Impedance

Output Impedance

Voltage-Series feedback

Increases

Decreases

Voltage-Shunt feedback

Decreases

Decreases

Current-Series feedback

Increases

Increases

Current-Shunt feedback

Decreases

Increases

 

‘Series’ increases Input impedance while 'Shunt' decreases it.

 

'Current' increases output impedance while ‘Voltage’ decreases it

 

Examples of Feedback

 

 

Voltage Series Feedback

 

 

 

 

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Current Series Feedback

 

 

 

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Voltage Shunt Feedback

 

 

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