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Chapter 4Common Diode ApplicationsClippers, Clampers, Voltage Multipliers, Displays, and

Logic Circuits

By jashvir chhikara

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Objectives

• State the purposes served by clippers, clampers, and voltage multipliers.

• Describe the operation of series and shunt clippers.

• Describe the effects of negative and positive clampers on an input waveform.

• Describe the use of the LED in multisegment displays.

• Study simple diode logic circuits.

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Fig 4.1-11 Clipper (limiter) circuits. (1)

Negative series clipper.

D1

RL

Vin Vin-0.7V

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Fig 4.1-11 Clipper circuits. (2)

Positive series clipper.

D1

RL-Vin

-Vin+0.7V

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Fig 4.1-11 Clipper circuits. (3)

Negative shunt clipper.

RS

D1 RL

IT

Vin(pk)in(pk)

L

L S

RV

R R

-0.7V

RS

D1 RL

IF

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Fig 4.1-11 Clipper circuits. (4)

Positive shunt clipper.

+0.7V

RS

D1RLIF

in(pk)L

L S

RV

R R

RS

D1 RL

IT

-Vin(pk)

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Fig 4.1-11 Clipper circuits. (5)

Biased shunt clipper.

VB

RS

RLVB + 0.7V

VB

RS

RL -VB - 0.7V

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Fig 4.1-11 Clipper circuits. (6)

Adjustable shunt clipper.

+VB

RS

RL

Vin

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Fig 4.12-13 Clipper applications. (1)

Transient-protection circuits

A

+5 V

D1

D2

Transient

+5 V

0 V

-5 V

On

ILReverse

Off

IL

ForwardFree-wheeling diode

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Fig 4.12-13 Clipper applications. (2)

AM detector

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Fig 4.14 Clampers (DC restorers).

Input signalsource

Positiveclamper

Load

0V 0V20Vpp

20Vpp

Input signalsource

Negativeclamper

Load

0V20Vpp 0V20Vpp

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Fig 4.15 Clamper operation. (1)

C1

D1 RL

+VS

TC = 5(RD1C1)

C1

D1 RL

-VS

TD = 5(RLC1)

Charge Discharge

TC << TD

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Example 4.5

Determine the capacitor charge and discharge times for the circuit represented in Fig. 4.15. Assume that the forward resistance of the diode (RD1) is 10 , RL = 10k, and C1 = 1F.

1 1

1

5 5 10Ω 1μF 50μs

5 5 10kΩ 1μF 50ms

C D

D L

T R C

T R C

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Fig 4.16 Clamper operation. (2)

D1 RL5 V

On

VC

VC5 V

D1 RL5 V

Off

+5 V

-5 V

0 V

-10 V

0 V

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Fig 4.17 Clamper circuits.

C1

D1 RL

C1

D1 RL

Negative clamper Positive clamper

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Fig 4.18-19 Biased clampers.

Biased clampers.

VZ

C1

D1 RL

C1

RLVZ

D1

VB

C1

D1

R1

RL-VB

C1

D1

R1

RL

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Fig 4.20 Voltage multipliers. (1)

Half-wave voltage doublers.

VS

C1

D1

D2

C2 RL

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Fig 4.21 Voltage multipliers. (2)

Operation of half-wave voltage doublers.

VS(pk)

C1 D1

D2

C2 RLOn

Off

IS IL

VS(pk)

VC2

VS(pk)

C1 D1

D2

C2 RLIS

Off

OnVS(pk)

VC2

VC2=2VS(pk)

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Fig 4.23 Full-wave voltage doubler.

VS

D1

D2

C1

C2

VS(pk)

VS(pk)

C3 2VS(pk) RL

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Cockcroft-Walton Circuit

vi

2vp

vp

2vp

2vp 2vp

5vp

4vp

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Fig 4.28-29 Multisegment displays.

a

g

d

b

c

dp

f

e

Common cathode

COM

a

b

c

d

COM

dp

g

f

e

7-segment display

16-segment alphanumeric

display

5x7 dot matrix display

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Diode Logic Circuits (1)

V1

V2

Vo

5V

R5k

V1 V2 Vo

0V 0V 0.7V

0V 5V 0.7V

5V 0V 0.7V

5V 5V 5V

AND function

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Diode Logic Circuits (2)

V1 V2 Vo

0V 0V 0V

0V 5V 4.3V

5V 0V 4.3V

5V 5V 4.3V

OR function

V1

V2

Vo

R10k

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Summary

• Clippers (limiters).• Clipper applications.• Clampers (dc restorers).• Voltage multipliers.• LED applications.• Diode logic circuits.