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Ch(1) Signal Processing Circuits ١ WAVESHAPING CIRCUITS Major virtue of electronic circuits the ease of Controlled Voltage current waveforms Some of the basic waveshaping functions radar pulse – train generator
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WAVESHAPING CIRCUITS - kau.edu.sa · Ch(1) Signal Processing Circuits ٢ Clipping ﺐﻳﺬﺸﺗ Removing F undesired portion of a signal The waveshape function performed by the

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Page 1: WAVESHAPING CIRCUITS - kau.edu.sa · Ch(1) Signal Processing Circuits ٢ Clipping ﺐﻳﺬﺸﺗ Removing F undesired portion of a signal The waveshape function performed by the

Ch(1) Signal Processing Circuits

١

WAVESHAPING CIRCUITS Major virtue of electronic circuits the ease of

Controlled Voltage current waveforms Some of the basic waveshaping functions

radar pulse – train generator

Page 2: WAVESHAPING CIRCUITS - kau.edu.sa · Ch(1) Signal Processing Circuits ٢ Clipping ﺐﻳﺬﺸﺗ Removing F undesired portion of a signal The waveshape function performed by the

Ch(1) Signal Processing Circuits

٢

Clipping تشذيب

Removing undesired portion of a signal The waveshape function performed by the circuit components arranging

Consisting diode resistance voltage source

Input signal V1 varies with time Output signal VD VR The sum of the voltage around the loop = zero

vD + vR = v1 – V

vR = v1 – V - vD

vD = v1 – V - vR

Page 3: WAVESHAPING CIRCUITS - kau.edu.sa · Ch(1) Signal Processing Circuits ٢ Clipping ﺐﻳﺬﺸﺗ Removing F undesired portion of a signal The waveshape function performed by the

Ch(1) Signal Processing Circuits

٣

The behavior of the circuit depends on the state of the diode switch (S)

(S) closed when vD + vR = v1 – V

positive Fig-b then vD =0 and

vR = v1 – V

(S) open vD negative

and

vR = 0 clipping the signal the battery shifts signal down

and

the diode cuts signal off

Page 4: WAVESHAPING CIRCUITS - kau.edu.sa · Ch(1) Signal Processing Circuits ٢ Clipping ﺐﻳﺬﺸﺗ Removing F undesired portion of a signal The waveshape function performed by the

Ch(1) Signal Processing Circuits

٤

Practice Problem 3-9 Homework

Common type of clipping

v2 = v1 v2 ∝ v1 up to V

(a) Desired transfer characteristic v2 versus v1 (b) Diode circuit

The bias voltage set so that DA conducts v1 > VA DB conducts v1 < - VB

VR = v2 – v1

When - VB < v1 < VA

DA DB don't conduct V2 = v1 = vo

Page 5: WAVESHAPING CIRCUITS - kau.edu.sa · Ch(1) Signal Processing Circuits ٢ Clipping ﺐﻳﺬﺸﺗ Removing F undesired portion of a signal The waveshape function performed by the

Ch(1) Signal Processing Circuits

٥

Clamping تثبيت

Provide satisfactory pictures TV receivers The peak values of v(t) clamped at

predetermined levels In passing through amplifiers dc reference level lost clamper return signal to its original form

Page 6: WAVESHAPING CIRCUITS - kau.edu.sa · Ch(1) Signal Processing Circuits ٢ Clipping ﺐﻳﺬﺸﺗ Removing F undesired portion of a signal The waveshape function performed by the

Ch(1) Signal Processing Circuits

٦

R small C charge up to +Vm of v1 When +v1 change to -v1 Vc = Vm diode prevents current flow in opposite direction

V2 = v1 - Vm

Signal form unaffected

dc = Vm positive peak clamped at zero

If Vm changes Vc changes v2 again touches the axis

If D reversed - Vm clamped at zero

If B in series with D the reference of v2 VB

Page 7: WAVESHAPING CIRCUITS - kau.edu.sa · Ch(1) Signal Processing Circuits ٢ Clipping ﺐﻳﺬﺸﺗ Removing F undesired portion of a signal The waveshape function performed by the

Ch(1) Signal Processing Circuits

٧

Clamping rectifying related waveshaping function combination D C

Rectifier

Variable component rejected dc value

transmitted Clamper

Variable component transmitted dc value

rejected

Homework P.P 3 – 10

Page 8: WAVESHAPING CIRCUITS - kau.edu.sa · Ch(1) Signal Processing Circuits ٢ Clipping ﺐﻳﺬﺸﺗ Removing F undesired portion of a signal The waveshape function performed by the

Ch(1) Signal Processing Circuits

٨

Differentiating

Circuit (a) provides v2 derivative of v1

v2 ∝ to the capacitor charging current in

response to a step of rectangular wave v1

Linear circuit transforms rectangular wave

into series of short pulse if

RC small compared to T the period of the

input wave

General operation Applying Kirchhoff's voltage law to the left-hand

loop v1 = vC + vR ≅ vC

Page 9: WAVESHAPING CIRCUITS - kau.edu.sa · Ch(1) Signal Processing Circuits ٢ Clipping ﺐﻳﺬﺸﺗ Removing F undesired portion of a signal The waveshape function performed by the

Ch(1) Signal Processing Circuits

٩

vR small compared to vC

v2 ∝ to the derivative v1

Integrating

If differentiating is possible integrating is also

dtd

RCdtd

RCRivv

dtd

Ci

vvR

vC

c

C

12 ≅===∴

=

Page 10: WAVESHAPING CIRCUITS - kau.edu.sa · Ch(1) Signal Processing Circuits ٢ Clipping ﺐﻳﺬﺸﺗ Removing F undesired portion of a signal The waveshape function performed by the

Ch(1) Signal Processing Circuits

١٠

Square wave of V applied long enough for cyclic operation to be established RC little grater than 1/2 T of the square wave C charged discharged on alternate 1/2 T v2 shown in Fig. b If RC large compared to T

Only straight portion of the exponential appears

∴ v2 sawtooth wave ∝ time

In general v1 = vR + vC ≅ vR = iR

If vC small compared to vR RC >T

Page 11: WAVESHAPING CIRCUITS - kau.edu.sa · Ch(1) Signal Processing Circuits ٢ Clipping ﺐﻳﺬﺸﺗ Removing F undesired portion of a signal The waveshape function performed by the

Ch(1) Signal Processing Circuits

١١

V2 ∝ ∫ v1

Op Amp Integrator

General feed back network contains C L R

C feedback element

V1 ≅ 0

n at ground potential

I1 ≅ 0

The sum of the I into n

∫ ∫≅= dtvRC

idtC

v 1211

Page 12: WAVESHAPING CIRCUITS - kau.edu.sa · Ch(1) Signal Processing Circuits ٢ Clipping ﺐﻳﺬﺸﺗ Removing F undesired portion of a signal The waveshape function performed by the

Ch(1) Signal Processing Circuits

١٢

Integrating each term with respect to time and solving

This an integrator device very useful in computing signal processing signal generating

Op Amp Differentiator

dtCRvdvor

dtdvC

Rv

oo

1

1

1

1 0 −==+

∫ +−= consanctadtvCR

v o 11

1

Page 13: WAVESHAPING CIRCUITS - kau.edu.sa · Ch(1) Signal Processing Circuits ٢ Clipping ﺐﻳﺬﺸﺗ Removing F undesired portion of a signal The waveshape function performed by the

Ch(1) Signal Processing Circuits

١٣

R C interchanged Differentiator device The sum of the current

Vo ∝ dvi

Differentiator device is not so useful as the integrator

dtdvRCvsolving

Rv

dtdvC o

o 11

11 0 −==+