Common Base (CB)

Input & Output Characteristics

COMMON BASE (CB)

Engr.Usman Ali Khan

CONTENTS

1. CB, CE and CC

2. CB Circuit

3. CB Input Characteristics

4. CB Output Characteristics

BJT CONFIGURATIONS• Common Base (CB)

• Common Emitter (CE)

• Common Collector (CC)

COMMON BASE (CB)

Input Output

B

E C

Base is common both to input signal and output signal

COMMON EMITTER (CE)

Emitter is common both to input signal and output signal

Input

Output

E

C

B

COMMON COLLECTOR (CC)

Collector is common both to input signal and output signal

Input

Output

E

C

B

CB VOLTAGES AND CURRENTS

E

C

B

E

C

B

NPN PNP

IB

IE

IC

IB

IE

IC

VBE = 0.7 VEB = 0.7

VBE = -VEB

CB INPUT CHARACTERISTICS

B

E C

VBE

IE

VBC

IC

Input SideOutput Side

To observe the behavior of Base-Emitter junction when VBC is fixed

CB INPUT CHARACTERISTICS

VBE

IE

VCB = 0VVCB = 10V

VCB = 25V

0.7

CB OUTPUT CHARACTERISTICS

B

E C

VBE

IE

VBC

IC

Input SideOutput Side

To observe the behavior of Base-Collector junction when IE is fixed

CB OUTPUT CHARACTERISTICS

VBC

IC

-1 0 5 10

IE = 1mA

IE = 2mA

IE = 3mA

IE = 4mA

Saturation Region

Active Region

Junction Forward Biased Junction

Reverse Biased

Break down Region or Punch Through Region (Depletion Regions Overlap)

HOME WORK• Example: 4.2, 4.3

• End Problems: 4.6 4.7

Input & Output Characteristics

COMMON EMITTER (CE)

CONTENTS

1. β

2. CE Configuration

3. CE Input Characteristics

4. CE Output Characteristics

CE CONFIGURATION

InputE

C

B

Output

VCE

VCB

VBE

IB

IE

ICIE = IC + IB

VCE = VCB + VBE

VCE = VCB + 0.7

Input Current = IB

Input Voltage = VBE

Output Current = IC

Output Voltage = VCE

B

C

BC

CBOBC

CBOBC

CBOBC

BCECBOC

ECBOC

CBOEC

EINJC

CBOINJCC

I

I

II

III

III

III

IIIII

III

III

II

III

1

11

1

1

1

11

)(

)(

IC = 1mAIB = 10 µAβ =?

CE INPUT CHARACTERISTICS

VBE

IB

VCE = 20V

VCE = 10V

0.7

CE OUTPUT CHARACTERISTICS

VCE

IC

5 10 15 20

IB = 10 µA

IB = 20 µ A

IB = 30 µ A

IB = 40 µ A

Saturation Region

Active Region

Junction Reverse Biased

Break down Region or Punch Through Region (Depletion Regions Overlap)

HOME WORK• CC Characteristics

• Example: 4.4 4.6

• End Problems: 4.8 4.17

HOME TASK

• Make CC(Common Collector) Configuration and draw input output characteristics…