Ch1 transistor as small signal amplifier

UTMUNIVERSITI TEKNOLOGI MALAYSIA

Chapter 1

Transistor As A Small Signal Amplifier

SEE 2253ELECTRONIC CIRCUITS

Norlaili Mat Safri, Ph.D

Outcome

CO1: Describe the basic laws and theorems of basic concept of amplifiers

CO2: Apply the basic laws, theorem and methods of analysis for solving various problems in electronic circuit

CO3: Analyze the procedure that should be taken in solving electric circuit using theorems and methods of analysis: Perform AC analysis on amplifiers at low, middle and high frequencies

CO4: Categorize and analyze negative feedback topologies


Contents

Intro to Amplifier Circuit

Basic Amplifier Circuit, Amplifier Parameters (Avoc, Av, Ai, Zi & Zo), Decibel (dB)

BJT as an amplifier

Mid freq. ac analysis using hybrid- model – CE, CC, CB

Frequency response: Analysis at low & high freq.

Short circuit current gain, Bode plot, Simulation using MultiSim



Amplifier is a system that can amplify weak electrical signal into strong one by increasing the power level of the weak input signal.

Amplifier can amplify current, voltage, and/or power.


DC Supply Voltage

AmplifierInput signal Output signal

Vi Vo

Concept of small-signal amplifiers



Figure 1.1 : Examples of Amplifier Circuitry System

+ VCC

RB

RC

IC

RL VoVi

C1 C2IBii

io

IEBase/Tapak

Collector/Pemungut

Emitter/Pemancar

+ VDD (+12 V)

RD

ID

RL10k VoVi

C1

C2

IG

iiio

ZiZo

2.2k

CS RS750

RG10M

VGS

+ Vcc

V+

Vo

V-

- Vcc

RF

Av = infiniti

V1R1

V2R2

R3



Basic Amplifier Model

Figure 1.2 : Amplifier Model


Amplifier has 3 basic quantities (gain, A; input impedance, Zi, & output impedance, Zo).

Gain• Voltage gain :

• Current gain :

• Power gain :

i

OV V

VA

i

Oi I

IA

iVi

OP AA

P

PA



Gain (A)

• Av & Ai: refer to previous slide.

• AVOC? Zi? Zo?

Amplifier Parameters

(Avoc, Av, Ai, Zi & Zo)


Gain (A), in dB

Av (dB) = 20 log Av

If normalized,

Av (dB) = 20 log (Av/Avmax)

Decibel (dB)

How about current gain (Ai) and power gain (Ap)?


Basic Amplifier Circuit

Voltage amplifier

Current amplifier

Figure 1.3 : Amplifier Model



Figure 1.3 : Amplifier Model…cont.

Transconductance amplifier

Transresistance amplifier



Q. What is an amplifier?

1

Q. What is an ideal

amplifier?

2


Your Answers to Attributes of an Ideal Amplifier,

Basic Amplifier Model



Unloaded voltage gain

Keyword: Unloaded?

Figure 1.4 : Basic amplifier model (unloaded)



With loading effects

Keyword: Loaded?

Figure 1.5 : Basic amplifier model (loaded)

Technology

Ch1 transistor as small signal amplifier