ECE121: Electronics (1) : Lecture 2: Diode Clipping and Calmping Circuits

ECE121: Electronics (1)
Lecture 2: Diode Clipping and Calmping Circuits
Dr. Haitham El-Hussieny

Electronics and Communications Engineering
Faculty of Engineering (Shoubra)
Benha University
Spring 2017
Dr. Haitham El-Hussieny ECE121: Electronics (1) 1 / 17
Lecture Outline:
1 Introduction.
2 Diode Clipping Circuits.
3 Diode Clamping Circuits.

Introduction.
Table of Contents
1 Introduction.

Introduction.
Introduction:
Diode Clipper (Limiter):

Clippers or limiters are sometimes used to clip
off portions of signal voltages above or below Clipping
certain levels.

Introduction.
Introduction:
Diode Clipper (Limiter):

Clippers or limiters are sometimes used to clip
off portions of signal voltages above or below Clipping
certain levels.
Diode Clamper:
Clamper circuit is used to add or restore a dc
level to an electrical signal.
Clamping
Diode Clipping Circuits.
Table of Contents
1 Introduction.

Diode Clipping Circuits:

Positive Clipping:


Positive Clipping:
During the +ve half cycle:

The Diode is forward biased (ON) and
Vout = VD = 0.7 V (Clipped away!).

Positive Clipping:
During the +ve half cycle: During the -ve half cycle:
The Diode is forward biased (ON) and The Diode is reverse biased (OFF) and
Vout = VD = 0.7 V (Clipped away!). Vout = Vin (Remained!).

Negative Clipping:


Negative Clipping:
During the +ve half cycle:

The Diode is reverse biased (OFF) and
Vout = Vin (Remained!).

Negative Clipping:
During the +ve half cycle: During the -ve half cycle:
The Diode is reverse biased (OFF) and The Diode is forward biased (ON) and
Vout = Vin (Remained!). Vout = VD = 0.7 V (Clipped away!).
both Positive and Negative Clipping, a part of the output

voltage looks like the input voltage.
The output voltage magnitude determined by the voltage
divider formed by R1 and the load resistor, RL , as follows:
RL
Vout = Vin
R1 + RL
If R1 is small compared to RL , then Vout ≈ Vin .

Example
What would you expect to see displayed on an
oscilloscope connected across RL in the limiter shown ?
Solution:
The diode is forward-biased and conducts when the
input voltage goes below −0.7V . So, for the negative
clipper, the peak output voltage across RL is:
RL 100
Vp(out) = Vp(in) = 10 = 9.09 V
R1 + RL 100 + 10


Biased Clippers:
Biased Positive Clipper:

The level to which an ac voltage is clipped can be
adjusted by adding a bias voltage, VBIAS , in series
with the diode.
The voltage at point A must equal VBIAS + 0.7 V
before the diode will become forward-biased and
conduct.
Once the diode begins to conduct, the voltage at
point A is limited to VBIAS + 0.7 V so that all input
voltage above this level is clipped off.


Biased Clippers:
Biased Negative Clipper:

To limit a voltage to a specified negative level, the
diode and bias voltage must be connected as shown.
In this case, the voltage at point A must go below
−VBIAS − 0.7 V to forward-bias the diode and limit
the input voltage.


Biased Clippers:
Combination of Positive and Negative Clippers:

1 When the voltage at point A reaches
+5.7 V , diode D1 conducts and limits the
waveform to +5.7 V .
2 Diode D2 does not conduct until the
voltage reaches −5.7 V .
3 Therefore, positive voltages above +5.7 V
and negative voltages below −5.7 V are
clipped off.
Application: sinusoidal to square-wave
conversion.

Voltage Divide Biased Clippers:
To change the bias voltage value VBIAS , we can replace it by a resistive voltage divider.

Diode Clamping Circuits.
Table of Contents
1 Introduction.

Diode Clamping Circuits:

[1] Positive Clamper:
A clamper adds a positive dc level to an ac voltage.
During the -Ve half cycle: the diode is forward biased, allowing the capacitor to charge
to near the peak of the input
During the +Ve half Cycle: the diode is reverse-biased. The capacitor can only
discharge through the resistance of RL .
The amount that is discharged capacitor depends on the value of RL .

Diode Clamping Circuits:
[2] Negative Clamper:

A clamper adds a negative dc level to an ac voltage.
Discuss it’s operation by your self.

End of Lecture
Best Wishes
haitham.elhussieny@gmail.com

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ECE121: Electronics (1)

Lecture 2: Diode Clipping and Calmping Circuits

Dr. Haitham El-Hussieny

2 Diode Clipping Circuits.

3 Diode Clamping Circuits.

Dr. Haitham El-Hussieny ECE121: Electronics (1) 2 / 17

2 Diode Clipping Circuits.

3 Diode Clamping Circuits.

Dr. Haitham El-Hussieny ECE121: Electronics (1) 3 / 17

Diode Clipper (Limiter):

Dr. Haitham El-Hussieny ECE121: Electronics (1) 4 / 17

Diode Clipper (Limiter):

2 Diode Clipping Circuits.

3 Diode Clamping Circuits.

Dr. Haitham El-Hussieny ECE121: Electronics (1) 5 / 17

Diode Clipping Circuits:

Dr. Haitham El-Hussieny ECE121: Electronics (1) 6 / 17

Diode Clipping Circuits:

During the +ve half cycle:

Diode Clipping Circuits:

Diode Clipping Circuits:

Dr. Haitham El-Hussieny ECE121: Electronics (1) 7 / 17

Diode Clipping Circuits:

During the +ve half cycle:

Diode Clipping Circuits:

Diode Clipping Circuits:

both Positive and Negative Clipping, a part of the output

Dr. Haitham El-Hussieny ECE121: Electronics (1) 8 / 17

Diode Clipping Circuits:

Dr. Haitham El-Hussieny ECE121: Electronics (1) 9 / 17

Diode Clipping Circuits:

Biased Positive Clipper:

Dr. Haitham El-Hussieny ECE121: Electronics (1) 10 / 17

Diode Clipping Circuits:

Biased Negative Clipper:

Dr. Haitham El-Hussieny ECE121: Electronics (1) 11 / 17

Diode Clipping Circuits:

Combination of Positive and Negative Clippers:

Diode Clipping Circuits:

Dr. Haitham El-Hussieny ECE121: Electronics (1) 13 / 17

2 Diode Clipping Circuits.

3 Diode Clamping Circuits.

Dr. Haitham El-Hussieny ECE121: Electronics (1) 14 / 17

Diode Clamping Circuits:

Dr. Haitham El-Hussieny ECE121: Electronics (1) 15 / 17

Diode Clamping Circuits:

[2] Negative Clamper:

Discuss it’s operation by your self.

Dr. Haitham El-Hussieny ECE121: Electronics (1) 16 / 17

Dr. Haitham El-Hussieny ECE121: Electronics (1) 17 / 17

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