Experiment #3:
Clipper and Clamper Circuits
Friday Group
Dr. Somnath
Ari Mahpour
9-25-09 and 10-2-09
Teddy Ariyatham
Due 10-9-09
Jayson dela Cruz
Table of Contents
Objective .............................................................................................................................. 3
Tools .................................................................................................................................... 3
Theory .................................................................................................................................. 3
Preliminary Calculations ..................................................................................................... 4
Discussion and Results ........................................................................................................ 5
Steps 1 and 2: Single Positive Peak Clipper .................................................................... 5
Steps 3 and 4: Single Negative Peak Clipper .................................................................. 7
1 Volt Input: ................................................................................................................. 7
2 Volt Input: ................................................................................................................. 8
3 Volt Input: ................................................................................................................. 9
4 Volt Input: ............................................................................................................... 10
Step 5: Zener Diode Clipper (10V Input) ...................................................................... 11
Steps 6 and 8: Clamper Circuit ...................................................................................... 12
0.1 µF Capacitor:........................................................................................................ 12
470 µF Capacitor:....................................................................................................... 13
Step 7: Clamper Circuit ................................................................................................. 14
Step 9: Clamper Circuit (10µF): .................................................................................... 15
Conclusion ......................................................................................................................... 16
Objective
This laboratory experiment explores the applications of the diode. The purpose of this
experiment is to observe the clipping and clamping functions found in our circuit designs. The
designs that are required to be implemented and built is the zener diode clipper circuit and
various forms of the clamper circuit.
Tools
-
Oscilloscope
-
Functional generator
-
Power supply
-
Diodes: D1N4002 and D1N746A (zener)
-
Capacitors: 0.1 µF and 10µF
-
Resistors: 1kΩ and 15 kΩ
Theory
When observing the circuits, one can see that the both the clipping and clamping
functions will occur. Clipping entails that the ends of the wave forms become cut off or
“clipped.” There are several different cases that are explored in this experiment with respect to
clipping. A case of clipping would occur in the forward active region. For example, a diode’s
voltage threshold value is 0.7V. If one were to apply it across the diode, the clipping would
occur at 0.7V since that is its threshold voltage. By adding a battery, the threshold is raised.
Adding a 1V battery next to the diode will now create a total threshold voltage of 1.7V.
Applying anything greater than 1.7V as an input would cause a clipping at 1.7V. Anything less
than that threshold value will pass right through, thus resulting in no clipping occurring.
When introducing a capacitor into the circuit clamping occurs. This essentially shifts the
DC offset up or down depending on the direction of the diode. As we will see when testing
circuits with different capacitances, forward active mode will determine whether there will be a
full shift or if the circuit will be partially scaled down (i.e. squashed). The direction of the diode
will also determine whether there will be a positive or negative shift on the y-axis.
Preliminary Calculations
Discussion and Results
Steps 1 and 2: Single Positive Peak Clipper
Figure 2.1: PSPICE Model
12V
8V
4V
0V
-4V
-8V
-12V
0s
0.5ms
1.0ms
1.5ms
2.0ms
2.5ms
3.0ms
3.5ms
4.0ms
4.5ms
5.0ms
V(R1:2,0)
Time
Figure 2.2: PSPICE Simulation
The circuit in figure 2.1 is a positive peak clipper circuit. The reason the graph output
resembles a negative half wave rectifier is because the voltage measured is across the diode,
rather than a load resistor. When the diode is in forward bias, the positive portions of the wave,
the only voltage measured in the observable area is the +1Vdc source plus the diode voltage
which is 0.7V when forward biased. This accounts for the positive wave output of +1.7Vdc. The
oscilloscope images to the corresponding circuit can be found attached (Figure 1.1 and Figure
1.2).
Steps 3 and 4: Single Negative Peak Clipper
1 Volt Input:
Figure 4.1: PSPICE Model
1.0V
0.5V
0V
-0.5V
-1.0V
0s
0.5ms
1.0ms
1.5ms
2.0ms
2.5ms
3.0ms
3.5ms
4.0ms
4.5ms
5.0ms
V(R1:2,0)
Time
Figure 4.1b: PSPICE Simulation
The clipping circuit in figure 4.1 shows a negative peak clipper circuit, but the graph seems to
show the entire sine wave. The negative peak isn’t clipped because the input voltage wasn’t
greater than the 1.7V it would take to put the diode into linear/active mode. Therefore the
diode stays in saturation mode and the full 1V is read across the voltmeter leads.
2 Volt Input:
Figure 4.2: PSPICE Model
2.0V
1.0V
0V
-1.0V
-2.0V
0s
0.5ms
1.0ms
1.5ms
2.0ms
2.5ms
3.0ms
3.5ms
4.0ms
4.5ms
5.0ms
V(R1:2,0)
Time
Figure 4.2b: PSPICE Simulation
Figure 4.2 shows the same circuit as figure 4.1 except with a 2V input rather than a 1V
input. The positive section shows the full 2V amplitude because the diode is reverse biased. The
negative half of the wave is greater than the 1.7 volts required to activate the diode, but in the
process, it loses 1.7V of its potential, according to KVL. Therefore the difference between the
leads is -1.7V, resulting in a clipped sin wave.
3 Volt Input:
Figure 4.3: PSPICE Model
3.0V
2.0V
1.0V
0V
-1.0V
-2.0V
-3.0V
0s
0.5ms
1.0ms
1.5ms
2.0ms
2.5ms
3.0ms
3.5ms
4.0ms
4.5ms
5.0ms
V(R1:2,0)
Time
Figure 4.3b: PSPICE Simulation
Figure 4.3 shows the same circuit as figure 4.1 except with a 3V input rather than a 2V
input. The positive section shows the full 3V amplitude, while the bottom section again only
shows the -1.7V difference between the positive and negative leads.
4 Volt Input:
Figure 4.4: PSPICE Model
4.0V
2.0V
0V
-2.0V
-4.0V
0s
0.5ms
1.0ms
1.5ms
2.0ms
2.5ms
3.0ms
3.5ms
4.0ms
4.5ms
5.0ms
V(R1:2,0)
Time
Figure 4.4b: PSPICE Simulation
Figure 4.4 shows the same circuit as figure 4.1 except with a 4V input rather than a 3V
input. he positive section shows the full 3V amplitude, while the bottom section again only
shows the -1.7V difference between the positive and negative leads. This circuit is always going
to be clipped at -1.7V because any voltage greater than 1.7V will activate the diode, therefore
negating any difference in potential between the two voltmeter leads.
Step 5: Zener Diode Clipper (10V Input)
Figure 5.1: PSPICE Model
4.0V
2.0V
0V
-2.0V
-4.0V
0s
0.5ms
1.0ms
1.5ms
2.0ms
2.5ms
3.0ms
3.5ms
4.0ms
4.5ms
5.0ms
V(D1:2,0)
Time
Figure 5.2: PSPICE Simulation
Figure 5.1 is a zener diode clipper circuit. Zener diodes are diodes with a relatively low
breakdown voltage. This graph represents the voltage across a reverse biased zener diode until
the source voltage “overtakes” the zener breakdown voltage. Once this happens, the voltage
potential quickly flat-lines. According to the graph, the breakdown voltage of these zener
diodes is somewhere around 3V. When 10V positive is applied to the circuit, the 10V is read by
the positive lead, while 10V-0.7V-3V = 6.3V is read across the output. This causes a voltage
difference of 3.7 to be read as output, which is close to the value we obtained in the simulation.
Steps 6 and 8: Clamper Circuit
0.1 µF Capacitor:
Figure 8.1: PSPICE Model
20V
10V
0V
-10V
-20V
0s
0.5ms
1.0ms
V(C1:1,C1:2)
V(R1:2,0)
1.5ms
2.0ms
2.5ms
3.0ms
3.5ms
4.0ms
4.5ms
5.0ms
Time
Figure 8.2: PSPICE Simulation
Figure 8.1 is a clamper circuit that uses a diode and a capacitor to apply a dc offset to
the source wave. While the input wave is positive, all of the voltage goes into the capacitor,
which is why no voltage shows during the positive output portions. While the input wave is
negative, the capacitor discharges and stacks on top of the input, therefore amplifying it. This
explains why the negative peak is more than the 10V input wave.
470 µF Capacitor:
Figure 8.3: PSPICE Model
20V
10V
0V
-10V
-20V
0s
0.5ms
1.0ms
V(C1:1,C1:2)
V(C1:2,0)
V(C1:1,0)
1.5ms
2.0ms
2.5ms
3.0ms
3.5ms
4.0ms
4.5ms
5.0ms
Time
Figure 8.4: PSPICE Simulation
This clamper circuit is identical to the previous clamper circuit, except that the capacitor
has a greater capacitance, therefore holds more charge. During the first positive half wave, the
capacitor becomes charged with 10V. From that point on, the capacitor acts like a battery,
shifting the entire waveform down by 10V.
Step 7: Clamper Circuit
As seen in figure 7.1 (attached) the 10 µF caused a vertical shift. As
opposed to the previous two clamper circuits, this shift is neither negative nor a
positive with a cutoff, rather it merely has a positive vertical shift. The peak-topeak voltage is approximately the same, therefore, with respect to that nothing
has changed, however, the DC offset must be considered. This capacitance value
was just perfect to cause a DC offset of 10 volts.
Step 9: Clamper Circuit (10µF):
Figure 9.1: PSPICE Model
20V
10V
0V
-10V
-20V
0s
0.5ms
1.0ms
V(C1:1,C1:2)
V(C1:2,0)
V(C1:1,0)
1.5ms
2.0ms
2.5ms
3.0ms
3.5ms
4.0ms
4.5ms
5.0ms
Time
Figure 9.2: PSPICE Simulation
This clamper circuit act the same as the previous clamper circuit figure 8.3 except that
the diode direction is flipped, and a battery is added behind the diode. Therefore the shifted
value will be the capacitor charge (10V) - 0.7 voltage across the diode, - 1Vdc because of the
battery. 10-.7-1 = 8.3V DC offset.
Conclusion
This laboratory experiment taught us many things about certain circuits,
but more than that, it taught us how to problem solve. When running into various
problems, we would pull out our notes from the corresponding lecture class and
dissect the physics of all the units that were under testing. By following charts,
equations, and lecture examples we were able to get through the experiment
with a deep understanding of the material that had to be covered throughout the
course of this experiment. In the work field we will find that this will frequently be
the case, therefore, learning this skill before going out into the field is integral.
Thus, we are brought here to gain these skills so we will be properly prepared to
join the workforce when we finish our academic career here at California State
University, Northridge.