What are clippers circuits?

download report

Transcript What are clippers circuits?

Clipper circuits
LET’S REMOVE UNWANTED PART OF SIGNALS
1.
2.
3.
4.
5.
6.
What are clipper circuits?
Types of clipper circuits.
Unbiased positive clipper.
Unbiased negative clipper.
Biased series positive clipper.
Biased series negative clipper.
 Clipper
circuits are used to remove the part of a signal
that or above or below some defined reference level.
 One of the simple example of a clipper is the half-wave
rectifier that circuit basically cut off everything at the
reference level of zero and let only the positivegoing(negative-going) portion of the input waveform
through.
 Clipping circuits(also known as limiters, amplitude
selectors or slicers )
1)
Unbiased clipper circuits
•
•
2)
Unbiased positive clipper
Unbiased negative clipper
Biased clipper circuits
•
•
biased positive clipper
biased negative clipper
Note:
In all the explanations we have considered the diode
to be ideal.


Positive clippers are used to clip positive portions
of the input signal and allow the negative portions
of the signal to pass through.
Figure below shows the input and output signal
along with the positive clipper. The positive cycle is
completely clipped off by the clipper.

Section (b) shows the same clipper configuration as it is shown
in (a).but the diodes is replaced with its equivalent circuit
model. When the input signal goes positive, the cathode
terminal of diode attains a higher potential than anode. This
makes the diode reverse biased. The diode in reverse biased
configuration can be modeled as an open switch. No current
flows through the load and hence no output appears across the
load. This is the reason why the positive cycle is completely
clipped off.


Negative clippers are used to clip negative portions
of the input signal and allow the positive portions of
the signal to pass through.
Figure below shows the input and output signal
along with the negative clipper. The negative cycle
is completely clipped off by the clipper.

Section (b) shows the same clipper configuration as it is shown
in (a).but the diodes is replaced with its equivalent circuit
model. When the input signal goes positive, the anode terminal
of diode attains a higher potential than cathode. This makes the
diode forward biased. The diode in reverse biased configuration
can be modeled as an closed switch. No current flows through
the load and hence no output appears across the load. This is
the reason why the negative cycle is completely clipped off.

As shown earlier, we saw the clipping of the signal
takes place as soon as input signal goes positive. If
we want to change the clipping level of AC voltage,
then external biasing voltage must be used. the figure
given below shows a biased(series) clipper.

As shown earlier, we saw the clipping of the signal
takes place as soon as input signal goes negative. If
we want to change the clipping level of AC voltage,
then external biasing voltage must be used. the figure
given below shows a biased(series) clipper.
•
•
•
•
Clamper is a network constructed of a diode, a
resister and a capacitor that shifts a waveform to a
different level without changing the appearance of the
applied signal.
A clamper adds a dc voltage to the signal
A positive clamper shifts its input waveform in a
positive direction, so that it lies above a dc reference
voltage.
A negative clamper shifts its input waveform in a
negative direction, so that it lies below a dc reference
voltage.
• On the first
negative half
cycle of the input
the diode is
turned on.
• At negative peak
capacitor is fully
charged to Vp.
•
Diode is off
• RLC is made
much larger than
the time period
of the signal.
• Stiff Clamper
RLC > 100T
• Due to this
reason capacitor
remains fully
Charged During
off time of diode
•
•
•
•
•
•
Clampers are used in
test equipment
radar systems,
electronic counter measure systems
sonar systems.
These are commonly used in analog television
receivers to restore the DC component of the video
signal.

In measuring non-sinusoidal signals such as square,
saw tooth etc .
VOLTAGE MULTIPLIER
Use clamping action to increase peak rectified
voltages without necessary to increase input
transformer’s voltage rating.
• Multiplication factors: two, three or four.
• Three types of voltage multipliers:
•
Voltage doubler
1.
Half – wave voltage doubler
2.
Full – wave voltage doubler

Voltage tripler

Voltage Quadrupler
• Voltage multipliers are used in high-voltage, low
current applications, i.e. TV receivers.
•
Half-wave voltage Doubler:

Clamping action can be used to increase peak
rectified voltage. Once C1 and C2 charges to the peak
voltage they act like two batteries in series,
effectively doubling the voltage output. The current
capacity for voltage multipliers is low.
Full-wave voltage doubler:

Arrangement of diodes and capacitors takes
advantage of both positive and negative peaks to
charge the capacitors giving it more current capacity.
 Voltage
triplers and quadruplers utilize three and
four diode capacitor arrangements, respectively.
 Voltage
tripler and quadrupler gives output 3Vp and
4Vp, respectively.
 Tripler
output is taken across C1 and C3, thus Vout =
3Vp
 Quadrupler
output is taken across C2 and C4 , thus
Vout = 4Vp
 PIV for
both cases: PIV = 2Vp
Voltage Triple
Voltage Quadruple