CLIPPERS

Module 5

By

Dr. Bernie Redoña

Reference: Electronic Devices and Circuit Theory by Boylestad & Nashelsky, 10 th Ed

1. Design a clipper circuit given an

output and an input.

LEARNING OUTCOMES:

output and an input.

2. Predict and analyze the output

response of a clipper circuit.

2

Clippers are networks that employ diodes to “clip” away a portion of an input signal without distorting the remaining part of the applied waveform.

I. What are clippers???

RvO

++

v i

3

The half wave rectifier shown is the simplest form of diode clipper.

There are no boundaries on the type of signals that can be applied to a clipper.

Clippers can be series or parallel.

--

I. CLIPPERS

t

Vo

0

V

Tt

Vi

0

V

-V ++

4

t

Vo

0

V

Tt

Vi

0

V

-V

RvO

+

--

v i

I. CLIPPERS: A. Series Configuration with DC Supply

++ V + -Vi

V m

5

RvO

--

v i T2

Tt

0

I. CLIPPERS: A. Series Configuration with DC Supply

RvO

++

--

v i

V + -

tT2

T

Vi

0

V m1. Take careful note where the output voltage is defined

- In this case, it is directly across the

6

2. Try to develop an overall sense of the response b y simply noting the “pressure” established by each supply and the effect it will have on the conventio nal current direction through the diode.

- Any supply voltage greater than V volts will turn the diode on and conduction can be established through the load resi stor.

- In this case, it is directly across the resistor R.

I. CLIPPERS: A. Series Configuration with DC Supply

RvO

++

--

v i

V + -

tT2

T

Vi

0

V m

3. Determine the applied voltage (transition voltage) that will result in a change state for the diode from the “off” to the “on” state.

- For ideal diode, this will occur when VD=0 V, and ID = 0 mA. Hence v i = V

7

VD=0 V, and ID = 0 mA. Hence v i = V

R vO = iR R = idR = (0)R = 0 V

++

--

v i

V

+ -

V d = 0 V id = 0 A

vO = v i – V (ON region )

vO = 0 V (OFF region )

I. CLIPPERS: A. Series Configuration with DC Supply

3. Determine the applied voltage (transition voltage) that will result in a change state for the diode from the “off” to the “on” state.

- For ideal diode, this will occur when VD=0 V, and ID = 0 mA. Hence v i = V

t

T T

Vi

0

V m

Von

off

8

VD=0 V, and ID = 0 mA. Hence v i = V

R vO = iR R = idR = (0)R = 0 V

++

--

v i

V

+ -

V d = 0 V id = 0 A

vO = v i – V (ON region )

vO = 0 V (OFF region )

T2

T0

I. CLIPPERS: A. Series Configuration with DC Supply

4. Draw the output waveform directly below the applied voltage using the same scales for the horizontal axis and the vertical axis.

- The output voltage when the applied voltage has its peak value.

t

T2

T

Vi

0

V m

9

RvO

++

--

v i

V + -

voltage has its peak value.

vOpeak = Vm – V

T2

T

Vo

0

V m - V

2

EXAMPLE: Clippers- Series Configuration

1. Determine the output waveform for the sinusoidal input.

Vi20 V

++ 5 V+ -

10

T2

Tt

0

R vO

--

v i

2 KΩ

EXAMPLE: Clippers- Series Configuration

2. Determine the output waveform for the given input.

Vi20

++ 5 V+ -

11

T2

T t0

R vO

--

v i

2 KΩ

-10

I. CLIPPERS: B. Parallel Configuration

R ++Vi

V m

12

vO

--

v i T2

Tt

0

t

Vo

0

V

Tt

Vi

0

V

-V

I. CLIPPERS: B. Parallel Configuration

R ++

13

t

Vo

0

V

Tt

Vi

0

V

-V

vO

--

v i

EXAMPLE: Clippers- Parallel Configuration

1. Determine the output waveform for the given input.

Vi

16 VR

++

14

t0

16 V

-16 V

R

vO

-

4 V +

--

v i

1. Take careful note where the output voltage is defined

- The output is defined across the series combination of 4 -V supply and the diode

tt

Vi

0

16 V

-16 V

R

vO

+

-

4 V

+

-

+

-

v i

EXAMPLE: Clippers- Parallel Configuration

15

2. Try to develop an overall sense of the response.

- The polarity of the dc supply and the direction of the diode strongly suggest that the diode will be in the “on” state for a good portion of the negative region of the input signal.

- Since the output is directly across the series com bination, when the diode is in its short-circuit state, the output vol tage will be directly across the 4-V supply.

combination of 4 -V supply and the diode

3. Determine the transition level.

- For ideal diode, this will occur when VD=0 V, and ID = 0 mA. Hence v i = 4 V

VR = 0 Vt

t

Vi

0

16 V

-16 V

R

vO

+

-

4 V

+

-

+

-

v i

EXAMPLE: Clippers- Parallel Configuration

16

v i = 4 V

V

Vd = 0 V id = 0 A

vO

+

-

4 V +

-

+

-

v i

V --

4. Draw the output waveform directly below the applied voltage using the same scales for the horizontal axis and the vertical axis.

EXAMPLE: Clippers- Parallel Configuration

t

Vi

0

16 V

17

- The transition level is drawn along with V o = 4V when the diode is on.

For V i >= 4V, Vo = 4V

t

Vo

0

16 V

4 V

-16 V

EXERCISES:1. Determine Vo for the network.

Vi10 V

++

5 V

+ -

Si

18

T2

T t0

R vO

--

v i 4.7 KΩ

-10 V

EXERCISES:2. Sketch Vo for the network.

Vi8 V ++ 2.2 KΩ

Si

19

t0

-8 V

vO

-

4 V +

--

v i

20

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21

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