In this tutorial we will learn the following knowledge:
Use semiconductor diodes to convert AC to DC signals.
Use capacitors with diodes to double the magnitude of a signal.
Basic Qucs management as a simulation tool for electronic circuits.
Analysis of circuits with non-linear devices.
Handling of linear and non-linear electronic components (Diodes and Condensers).
Knowledge of circuit analysis.
Basic knowledge of the Qucs.
Greetings the following tutorial for Utopian, from the account 
In this opportunity we will work with semiconductor diodes, to analyze an electronic circuit that doubles the magnitude value of an analog signal. Next, the circuit that we want to analyze is observed.
Today we will have to learn how to build a voltage duplicator circuit in Qucs simulator; this circuit is used to generate the high voltage required in cathode ray tubes, X-ray tubes, to power photomultipliers for gamma ray detectors. It is also used for the generation of high voltages for high-energy physics experiments. In the following image, the basic circuit with double voltage (with two diodes and two capacitors):
The following steps describe the use of the Qucs to perform the simulation of the circuit with voltage doubler:
Step 1: We opened the Qucs simulator. In the following image you can see the different Qucs windows, the most relevant ones are described below:
a. Project exploration window.
b. Schematic window of the circuit.
c. Tabs to select components.
d. Menu of connection and execution applications.
Step 2: The program is ready to use, in our case, we are going to build a duplicator circuit, which will transform the signal from alternating current to direct current. We proceed to select the components.
Step 3: We search our circuit power source, displacing components list and select “SOURCES” .
Step 4: Select "AC SOURCE", locate it in the schematic window and double click on the AC source to change its properties. We establish the voltage value and the frequency value. In our circuit, we use the 60 Hz frequency and the 10 Vp voltage.
Step 5: We return to the components menu and look for the capacitors, these elements are responsible for storing the voltage coming from the AC source.
Step 6: The capacitors will have an approximate value of 10 micro farad (µF), which generates enough time delay to store the voltage level it receives from the AC source before it can be discharged. Next we connect the capacitors with the AC source, and look for the diodes in the non-linear devices.
Step 7: After locating the diodes in the circuit, the earth node of the circuit is connected and two nodes with labels are created to visualize the input signal and the output signal of the voltage duplicator circuit.
Step 8: Displace the list and click on “SIMULATIONS” and Select “TRANSIENT SIMULATION”, transient analysis of voltage versus time will be held.
Step 9: The transient simulation must be configured. To do this, you must verify the frequency of the signal, choose the scanning of the analysis, so that the output signal can be displayed correctly.
Step 10: Click on "SIMULATE", save the file and then select from the menu the option "DIAGRAMS", then select the "CARTESIAN" mode, to activate the Cartesian graph where we will visualize the response of the circuit. Place the graphic in the new simulation window with extension .dpl.
Step 11: A single window is used to visualize the input signal and the output signal in the same graph as a function of time, for this the labels of the nodes that were connected in the schematic circuit are selected.
Step 12: Finally we have the graphic of the signal duplicated and stabilized. We can see than our entry source was 10Vp and our exit source is 20Vp. The voltage duplicator circuit converts the AC signal into a DC signal, based on the use of the rectifier diodes, to allow or block each peak of the signal and store its voltage level in the capacitors, the circuit shows the output the sum of the values stored by both capacitors, generating the effect of duplicating the tension.
The schematic circuit editing code is attached below. This code describes node by node the location and connection of each of the components of the circuit.
<Components>
<C C1 1 360 140 17 -26 0 1 "10 uF" 1 "" 0 "neutral" 0>
<Diode D1 1 220 100 -26 -31 0 2 "1e-15 A" 0 "1" 0 "10 fF" 0 "0.5" 0 "0.7 V" 0 "0.5" 0 "0.0 fF" 0 "0.0" 0 "2.0" 0 "0.0 Ohm" 0 "0.0 ps" 0 "0" 0 "0.0" 0 "1.0" 0 "1.0" 0 "0" 0 "1 mA" 0 "26.85" 0 "3.0" 0 "1.11" 0 "0.0" 0 "0.0" 0 "0.0" 0 "0.0" 0 "0.0" 0 "0.0" 0 "26.85" 0 "1.0" 0 "normal" 0>
<GND * 1 130 270 0 0 0 0>
<C C2 1 360 230 17 -26 0 1 "10 uF" 1 "" 0 "neutral" 0>
<Diode D2 1 240 270 -26 15 0 0 "1e-15 A" 0 "1" 0 "10 fF" 0 "0.5" 0 "0.7 V" 0 "0.5" 0 "0.0 fF" 0 "0.0" 0 "2.0" 0 "0.0 Ohm" 0 "0.0 ps" 0 "0" 0 "0.0" 0 "1.0" 0 "1.0" 0 "0" 0 "1 mA" 0 "26.85" 0 "3.0" 0 "1.11" 0 "0.0" 0 "0.0" 0 "0.0" 0 "0.0" 0 "0.0" 0 "0.0" 0 "26.85" 0 "1.0" 0 "normal" 0>
<Vac V1 1 130 180 18 -26 0 1 "10 V" 1 "60" 0 "0" 0 "0" 0>
</Components>
<Wires>
<360 100 360 110 "" 0 0 0 "">
<250 100 360 100 "" 0 0 0 "">
<360 170 360 200 "" 0 0 0 "">
<360 260 360 270 "" 0 0 0 "">
<270 270 360 270 "" 0 0 0 "">
<130 270 210 270 "" 0 0 0 "">
<130 210 130 270 "" 0 0 0 "">
<130 100 190 100 "" 0 0 0 "">
<130 100 130 150 "" 0 0 0 "">
<360 260 360 260 "Output" 390 230 0 "">
<130 100 130 100 "Input" 160 70 0 "">
</Wires>
<Diagrams>
</Diagrams>
<Paintings>
We're done! I hope this information will help you in your career. Thanks for reading me. See you soon in my next tutorial.