SWITCHING DC TWO-PORT NETWORKS
I. OBJECTIVES
a)To understand the link between the structure and the functions of two-port DC networks.
b)To understand the way to build up the voltage multipliers (double and triple) using simple two-port DC networks.
II. COMPONENTS AND INSTRUMENTATION
You will use the experimental assembly equipped with three semiconducting diodes of 1N4184 type (the stripe indicates the cathode) and three 100nF capacitors. Because you will apply and measure both dc and ac voltages you will need a dc regulated voltage supply, a signal generator, a digital multimeter and a dual channel oscilloscope.
III. PREPARATION
1.P. TEMPORAL MAXIMUM TWO-PORT NETWORK
1.1.P. WAVE FORMS and the operation of the circuit
The exercises in this paragraph will be solved using the ideal and voltage drop diode models.
How do the waveforms for vO(t) and vD(t) look like, in steady state, for the circuit shown in Fig.3.1 if vI (t)=5V d.c.?
How do the waveforms for vO(t) and vD(t) look like, in steady state, for the circuit shown in Fig.3.1 if vI (t) is a sinusoidal voltage with 10V, 1V, and 0.3V amplitudes?
How do the waveforms for vO(t) and vD(t) look like, in steady state, for the circuit if vI (t) is a rectangular voltage varying between 0V and 5V?
2.P. TRANSLATION TWO-PORT DC NETWORK (towards positive values)
2.1.P. WAVE FORMS and the operation of the circuit
The exercises in this paragraph will be solved using the ideal and voltage drop diode models.
How do the waveforms for vO(t) and vC(t) look like, in steady state, for the circuit shown in Fig.3.2 if vI (t)=-5V d.c.?
How do the waveforms for vO(t) and vC(t) look like, in steady state, for the circuit shown in Fig.3.2 if vI (t) is a sinusoidal voltage with 10V, 1V, and 0.3V amplitudes?
How do the waveforms for vO(t) and vC(t) look like, in steady state, for the circuit if vI (t) is a rectangular voltage varying between 0V and 5V?
3.P. VOLTAGE DOUBLER
3.1.P. WAVEFORMS and the operation of the circuit
How do the waveforms for vO1(t) and vC1(t) look like, in steady state, for the circuit shown in Fig.3.3 if vI (t) is a sinusoidal voltage with 10V amplitude?
How do the waveforms for vO(t) and vD2(t) look like, in steady state, for the circuit shown in Fig.3.3 for the above conditions?
How can you build the circuit shown in Fig. 3.3 using the circuits shown in Fig. 3.1 and Fig. 3.2?
4.P. VOLTAGE TRIPLER
4.1.P. The OPERATION of the circuit
What is the function of D1C1 group from the circuit shown in Fig. 3.4 consideringvI as input voltage and v1 as output voltage?
What is the function of D2C2 group from the circuit shown in Fig. 3.4 consideringv1 as input voltage and v2 as output voltage?
What is the function of D3C3 group from the circuit shown in Fig. 3.4 consideringv2 as input voltage and v3 as output voltage?
What is the value ofvO for the circuit shown in Fig. 3.4 if the amplitude of the sinusoidal input voltage is 10V?
How can we obtain an “n” times multiplier of the amplitude of the input voltage for n=4? But for n=5?
IV. EXPLORATIONS AND RESULTS
1. TEMPORAL MAXIMUM TWO-PORT NETWORK
1.1 WAVEFORMS and the operation of the circuit
Exploration:
Build the circuit shown in Fig. 3.1.
You will apply at the input a 5V d.c. voltage from dc regulated voltage supply.
VD and VO are measured using a digital multimeter.
Fig.3.1 Temporal maximum two-port
At the input of the circuit apply a sinusoidal voltage with 500 Hz frequency of and 10V amplitude obtained from the signal generator.
The signals vI and vO are displayed on the oscilloscope set in Y-t mode, both of the channels being directly coupled and having 0V in the centre of the screen. The two leads are connected in the points X, Y and the ground in the point G.
The measurements are done again for different amplitudes of vI: 1V, 0.3V.
At the input of the circuit apply a rectangular voltage varying between 0V and 5V with 500 Hz frequency of obtained from the signal generator (TTL signal).
vI and vO are visualized on the oscilloscope.
Results:
The values of vO and vD for vI =5V d.c.
The waveforms for vI(t), vO(t) and vD(t) considering the next values for the sinusoidal input voltage: 10V, 1V, and 0.3V. vD(t) is obtained from the difference between vI(t) and vO(t).
What the conclusions you came up with after you made the above points? Is there any difference between the value of the output voltage and the amplitude of the input voltage?
Draw the waveforms for vI(t), vO(t) and vD(t) for a rectangular input voltage varying between 0V and 5V.Interpret them.
Estimate the duration of the transient regime for the rectangular signal previously described.
How do you explain the operation of the circuit?
2. TWO-PORT TRANSLATION CIRCUIT (towards positive values)
2.1 WAVE FORMS and the operation of the circuit
Exploration:
Build the circuit shown in Fig. 3.2.
You will apply at the input a -5V d.c. voltage from a stabilised voltage source.
vD and vO are measured using a digital multimeter.
Fig. 3.2 Translation two-port
At the input of the circuit it is applied a sinusoidal voltage with frequency of 500 Hz and amplitude of 10V obtained from the signal generator.
The signals vI and vO are visualized on the calibrated oscilloscope set in Y-t mode, both of the channels being directly coupled and having 0V in the centre of the screen. The two leads are connected in the points X, Y and the ground in the point G.
The measurements are done again for different amplitudes of vI: 1V, 0.3V.
At the input of the circuit it is applied a rectangular voltage varying between 0V and 5V with frequency of 500 Hz obtained from the signal generator (TTL signal).
vI and vO are visualized on the oscilloscope.
Results:
The values of vO and vD for vI =5V d.c.
The waveforms for vI(t), vO(t) and vD(t) considering the following values for the amplitude of the sinusoidal input voltage: 10V, 1V, and 0.3V. vC(t) is computed as the difference between vI(t) and vO(t).
Specify the time evolution for the off and on state of the diode for each values of the amplitude of the input signal.
Considering the amplitude of the input signal to be 10V compare the voltage drop across D and C obtained in the previous section. What are your conclusions?
Draw the waveforms for vI(t), vO(t) and vD(t) for a rectangular input voltage varying between 0V and 5V.Interpret them.
Estimate the duration of the transient regime for the rectangular signal previously described.
How do you explain the operating principle of the circuit?
3. VOLTAGE DOUBLER
3.1 WAVEFORMS and the operation of the circuit
Exploration:
Build the circuit shown in Fig. 3.3.
Fig. 3.3 Voltage doubler
At the input of the circuit a sinusoidal voltage is applied with 500Hz frequency and 10V amplitude obtained from the signal generator.
vI(t) , vO1(t) and vO(t) are visualized on the oscilloscope. Because you can visualize only two signals simultaneously you will visualize first vI(t) and vO1(t) and then vI(t) and vO(t).
Be carefful when setting the oscilloscope (see previous sections).
Results:
Draw the waveforms for vI(t), vO1(t), vO(t), vC1(t) and vD2(t) for 10V amplitude of the input voltage.
How is the value of the dc output voltage compared with the amplitude of the input signal?
Explain the operation of the circuit taking into account the circuits shown previously in Fig.3.1 and Fig.3.2.
4. VOLTAGE TRIPLER
4.1 WAVEFORMS and the operation of the circuit
Exploration:
Build the circuit shown in Fig. 3.4.
At the input of the circuit a sinusoidal voltage is applied with 500Hz frequency and 10V amplitude obtained from the signal generator.
Using a digital multimeter as a d.c. voltmeter measure vC1, vC2 and vC3.
vI(t) and vO(t) are visualized on the oscilloscope.
The measurements are repeated for an input voltage of 1.7V amplitude.
Results:
Table with vC1, vC2 and vC3 and the amplitude of vO for values of 10V and 1.7V of the amplitude of vI.
How is the value of the dc output voltage with respect to amplitude value of input signal, for values of 10V and 1.7V of the amplitude of vI? Why?
Draw the waveforms for vI(t), v1(t), v2(t) and vO(t) for values of 10V and 1.7V of the amplitude of vI.
Show the on and off states of the diodes shown in Fig. 3.4 for values of 10V and 1.7V of the amplitude of vI.
How many DC groups do you think are needed to obtain a dc voltage of minimum 23V, if you have a variable voltage source with 6V amplitude?
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