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Parallel Clippers. Prepared By:Eng.Maira Naz Dated:01-08-2011. Applications of diode. Applications of Diodes. Clippers. Clampers. Peak Detectors. Voltage Multipliers. Simple Logic Gates. DC Power Supply. Filtering Circuits. Clippers. Clippers.

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Parallel clippers

Parallel Clippers

Prepared By:Eng.Maira Naz

Dated:01-08-2011



Applications of diodes
Applications of Diodes

  • Clippers.

  • Clampers.

  • Peak Detectors.

  • Voltage Multipliers.

  • Simple Logic Gates.

  • DC Power Supply.

  • Filtering Circuits.



Clippers1
Clippers

  • Clippers, limiters or clipping circuits make use of non-linear properties of diode, that is the diode conduct the current in forward direction and does not conduct in reverse direction.


Clippers2
Clippers

Basic operating Principle:

  • These circuits are primarily are wave shaping circuits.

  • They clip or remove certain portion of ac voltage applied to the input of circuit.


Clippers3
Clippers

Applications of Clippers:

  • They need to clip the voltage above or below a certain pre-determined voltage level arises in the television, digital computers, radar, and many other electronic circuits.


Clippers4
Clippers

Components of clipping circuits:

  • The clipping circuits used in electronics are not necessarily composed of simple diodes and resistors, they employ more advance components to do so.

  • The basic principle however remains the same.


Clippers5
Clippers

Steps to analyze clipper circuits.

  • Replace the diode by one of its equivalent models.

  • Identify ON and OFF states of diodes and clipping levels of Vin.

  • Derive the equation for transfer characteristics of the circuit.

  • Plot the transfer characteristics and input-output waveforms of the circuit.



Clippers7
Clippers

Further Classification:


Clippers8
Clippers

Further Classification (Cont..) :



Parallel clippers2
Parallel Clippers

Parallel Clippers:

  • The name parallel clipper stems from he fact that the diode is in parallel with load resistance.

    Unbiased Parallel Clipper:

  • In parallel unbiased clipper, there ia no battery connected in series with diode.



Parallel clippers3
Parallel Clippers

Unbiased Parallel Clipper:

Fig (a) Unbiased parallel clipper


Parallel clippers4
Parallel Clippers

Unbiased Parallel Clipper (Cont..):

  • Fig (a) shows, unbiased parallel clipper in which diode is connected in parallel with load resistance.


Parallel clippers5
Parallel Clippers

Unbiased Parallel Clipper (Cont..):

Fig (b) Input voltage waveform


Parallel clippers6
Parallel Clippers

Unbiased Parallel Clipper (Cont..):

  • Fig (b) shows the input voltage waveform that is going to apply at the input of the circuit shown in fig (a).

  • Mathematically it is represented by the following equation.

    Vin=VmaxSinωt


Parallel clippers7
Parallel Clippers

Observation for the analysis of clipping circuit:

  • Vmax should be greater than 0.7V built in potential of the silicon diode or 0.2 for germanium.

  • RL should be greater than Rin.

    RL>>Rin

    Or

    RL~10Rin

  • So, that the voltage drop across Rin can be neglected.



Parallel clippers8
Parallel Clippers clipping(Ideal diode)

Unbiased Parallel Clipper (Cont..):

Ideal Diode:

  • First, we should replace the given diode with an ideal one i.e., we should consider the ideal model of diode.


Parallel clippers9
Parallel Clippers clipping(Ideal diode)

Unbiased Parallel Clipper (Cont..):

Action during the positive half cycle:


Parallel clippers10
Parallel Clippers clipping(Ideal diode)

Unbiased Parallel Clipper (Cont..):

Action during the positive half cycle:

  • During the positive half cycle of the input voltage, the diode becomes forward biased and remains forward biased for entire half cycle of the input.


Parallel clippers11
Parallel Clippers clipping(Ideal diode)

Unbiased Parallel Clipper (Cont..):

Action during the positive half cycle:

  • As ideal diode acts as short circuit when forward biased, the current I flows entirely through diode.

  • The drop across short circuit diode is zero.


Parallel clippers12
Parallel Clippers clipping(Ideal diode)

Unbiased Parallel Clipper (Cont..):

Action during the positive half cycle:

  • As RL is in parallel with diode no current flows through it and output voltage Vo=0V.

  • This condition remains for entire positive half cycle of the input.

  • Thus positive half cycle gets clipped off.


Parallel clippers13
Parallel Clippers clipping(Ideal diode)

Unbiased Parallel Clipper (Cont..):

Action during the negative half cycle:


Parallel clippers14
Parallel Clippers clipping(Ideal diode)

Unbiased Parallel Clipper (Cont..):

Action during the negative half cycle:

  • During the negative half cycle, the diode is reverse biased and acts as open circuit.

  • The entire current flows through RL.

  • So, output voltage can be found by using VDR.

  • Vo = Vin RL/(Rin+RL)

    Where Vin= - Vm.

  • Since, RL>>Rin.

  • So, Rin can be neglected in comparison to RL.


Parallel clippers15
Parallel Clippers clipping(Ideal diode)

Unbiased Parallel Clipper (Cont..):

Action during the negative half cycle:

  • So, we can also write

    Vo=K Vin.

    Where K=RL/ Rin+RL.

  • So, during negative half cycle , proportionate negative half cycle is available at the output.

  • There exits a straight line relationship between input and output voltage.


Parallel clippers16
Parallel Clippers clipping(Ideal diode)

Unbiased Parallel Clipper (Cont..):

Output waveform:


Parallel clippers17
Parallel Clippers clipping(Ideal diode)

Unbiased Parallel Clipper (Cont..):

Transfer characteristics:

  • The graph of output variable against the input variable of the circuit is called as the transfer characteristics of the circuit.


Parallel clippers18
Parallel Clippers clipping(Ideal diode)

Unbiased Parallel Clipper (Cont..):

Equation for transfer characteristics:

  • Transfer Characteristic equation for the circuit shown in fig (a)

    Vo=0V …..for Vi ≥ 0V

    Vo=Vin RL/Rin+RL, …..for Vi < 0V


Parallel clippers19
Parallel Clippers clipping(Ideal diode)

Unbiased Parallel Clipper (Cont..):

Positive parallel Clippers:

  • Circuit shown in fig (a) is called as parallel clipper with positive clipping because it clips the positive half cycle of input voltage.



Parallel clippers20
Parallel Clippers clipping(Practical diode)

Unbiased Parallel Clipper (Cont..):

Practical silicon diode:

  • Now, we consider that the diode is not an ideal one and we must consider its 2nd model i.e., a Vd is connected in series with the diode.


Parallel clippers21
Parallel Clippers clipping(Practical diode)

Unbiased Parallel Clipper (Cont..):

Practical silicon diode:


Parallel clippers22
Parallel Clippers clipping(Practical diode)

Unbiased Parallel Clipper (Cont..):

Practical silicon diode:

Action during the positive half cycle


Parallel clippers23
Parallel Clippers clipping(Practical diode)

Unbiased Parallel Clipper (Cont..):

Practical silicon diode:

Action during negative half cycle


Parallel clippers24
Parallel Clippers clipping(Practical diode)

Unbiased Parallel Clipper (Cont..):

Practical silicon diode:

Input and output waveforms


Parallel clippers25
Parallel Clippers clipping(Practical diode)

Unbiased Parallel Clipper (Cont..):

Practical silicon diode:

  • Mathematically, it can be expressed as

    Vo=Vd …..for Vi ≥ Vd

    Vo=Vin RL/Rin+RL=Vin …..for Vi < Vd


Biased parallel clipper
Biased parallel clipper clipping(Practical diode)


Parallel clippers26
Parallel Clippers clipping(Practical diode)

Biased Parallel Clipper:

  • In parallel unbiased clipper, there is a battery connected in series with diode


Parallel clippers27
Parallel Clippers clipping(Practical diode)

Analysis of biased parallel clipper:

Ideal Diode:


Parallel clippers28
Parallel Clippers clipping(Practical diode)

Analysis of biased parallel clipper:

Ideal Diode:

  • In case of ideal diode, Vd=0V and VBB is connected in series with diode as it is biased parallel clipper.

  • Now, the battery voltage will appear at one side of diode and input voltage will appear across the other side of diode.


Parallel clippers29
Parallel Clippers clipping(Practical diode)

Analysis of biased parallel clipper:

Ideal Diode:

  • Diode will be the forward biased during the time interval whenever the Vin is greater than VBB.

  • Diode will be the reverse biased during the time interval whenever Vin is less than VBB.


Parallel clippers30
Parallel Clippers clipping(Practical diode)

Analysis of biased parallel clipper:

Ideal Diode:

During positive half cycle


Parallel clippers31
Parallel Clippers clipping(Practical diode)

Analysis of biased parallel clipper:

Ideal Diode:

Output waveform during negative half cycle


Parallel clippers32
Parallel Clippers clipping(Practical diode)

Analysis of biased parallel clipper:

Ideal Diode:

During the negative half cycle


Parallel clippers33
Parallel Clippers clipping(Practical diode)

Analysis of biased parallel clipper:

Ideal Diode:

Output waveform during negative half cycle



Parallel clippers34
Parallel Clippers clipping(Practical diode)

Analysis of different biased parallel clipping circuits:

Case 1:


Analysis of different biased parallel clipping circuits (Cont..):

Transfer characteristics equation for case 1:

Vo=Vin…..for Vin < VBB i.e. Vin<2.5 Vo=VBB=2.5V…..for Vin >VBB i.e. Vin ≥ 2.5


Parallel clippers35
Parallel Clippers (Cont..):

Analysis of different biased parallel clipping circuits (Cont..):

Case 2:


Parallel clippers36
Parallel Clippers (Cont..):

Analysis of different biased parallel clipping circuits (Cont..):

Transfer characteristics equation for case 2:

Vo=Vin…..for Vin < VBB i.e. Vin<-2.5 Vo=VBB= -2.5V…..for Vin ≥ VBB i.e. Vin ≥ -2.5


Parallel clippers37
Parallel Clippers (Cont..):

Analysis of different biased parallel clipping circuits:

Case 3:


Parallel clippers38
Parallel Clippers (Cont..):

Analysis of different biased parallel clipping circuits (Cont..):

Transfer characteristics equation for case 3:

Vo=Vin…..for Vin >VBB i.e. Vin> 2.5 Vo=VBB= 2.5V…..for Vin ≤VBB i.e. Vin ≤ 2.5


Parallel clippers39
Parallel Clippers (Cont..):

Analysis of different biased parallel clipping circuits (Cont..):

Case 4:


Parallel clippers40
Parallel Clippers (Cont..):

Analysis of different biased parallel clipping circuits (Cont..):

Transfer characteristics equation for case 4:

Vo=Vin…..for Vin >VBB i.e. Vin> -2.5 Vo=VBB= -2.5V…..for Vin ≤VBB i.e. Vin ≤ -2.5


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