Using Orcad Capture and PSpice for Circuit Design: A Step-by-Step Guide, Study Guides, Projects, Research of Electrical and Electronics Engineering

Download Using Orcad Capture and PSpice for Circuit Design: A Step-by-Step Guide and more Study Guides, Projects, Research Electrical and Electronics Engineering in PDF only on Docsity! Orcad Capture and PSpice The programs we will be using are Orcad Capture and PSpice A/D. The Capture program is used primarily used for drawing schematics. In Capture, you select parts from a set of libraries, and wire them together with a wire tool. Capture will automatically create a file used by PSpice to simulate this circuit. PSpice is the simulation program which provides the results of the circuit simulation. Today, we will be constructing an op amp circuit and testing it. Getting Started 1. Open Orcad Capture. To get to Capture, go to Start All Programs EE Programs PSpice Student Capture Student 2. From the File menu of Capture, choose New Project. A wizard will pop up. Select the ‘Analog or Mixed A/D’ radio button. Give your project an appropriate name. Then click ‘OK’. Next, select the ‘Create a blank project’ radio button, and click ‘OK’. 3. At this point, two windows will appear. The large mostly blank window is where you will draw the schematic. The smaller window on the left is there to help you keep track of your different project files. Click on the schematic window. Notice that a small, vertical bar appears on the right side of the screen. These are the tools for drawing the schematic. \ Figure 1. The parts of the Capture window Building the First Circuit 4. The first part we will select is a voltage source. On the right side tool bar, select the second button from the top, entitled ‘Place Part’, or go up to the Place menu and select Part. The parts are sorted into ‘libraries’ Libraries categorize parts so that they can be located easily. Voltage sources lie in the ‘sources’ library. Highlight the ‘SOURCE’ library. The part we are looking for is VDC. This is a DC voltage source, like a battery. Figure 2. The Place Part Menu 5. Highlight the VDC object, then click ‘OK’. Next, click somewhere on the white space of the schematic window. This will place the VDC on the screen. Notice the two texts next to the VDC symbol. The ‘0Vdc’ tells the voltage value of the source. The V1 is the name of the source. 6. Next go back into the Place Part menu. This time, highlight the ‘ANALOG’ library, and select the ‘R’ part, which is a resistor. Place the part next to the voltage source. Now that we have a couple parts, we want to wire them together. Select the Place Wire button, located right below the ‘Place Part’ button on the tools bar. Click on one end of the voltage source, and then move the wire and click on one end of the resistor. Next, wire the other end of the VDC to the other end of the resistor. Using Integrated Circuits in Capture 12. Next, create the op amp circuit. The first part will be to make an inverting amplifier. An inverting amplifier will take some input, and output the same signal inverted, and multiplied by a factor of A. This circuit will require 2 resistors, one operation amplifier, and one voltage source. The op amp used in this tutorial is the LM324. This part is in a library titled ‘EVAL’. To get the part, go to Place Part, and highlight the ‘EVAL’ library. Double-click on the LM324, and place it on your schematic. It will be easier to draw the circuit if the negative terminal of the op amp is on the top. To do this, right-click the LM324 you’ve placed, and select Mirror Vertically. 13. Place two resistors on the schematic. Also, place a 0-ground. Now, wire the resistors and ground as shown below. Note that the ground connects directly to the positive terminal. Figure 7. The op amp configuration for the inverting amplifier 14. A new type of voltage source will be used as the input for this circuit. Go to Place Part, and highlight the ‘SOURCE’ library. This time, select the ‘VSIN’ part. This part allows you to generate a sine wave voltage, where you specify the frequency, amplitude and offset. Double-click on each of the values and set them to the following: VOFF = 0 VAMPL = .1 FREQ = 1K Notice that commonly used letters can be substituted in for the values. For instance, 1K = 1000 Hz in the FREQ parameter for VSIN. Here is a list of commonly used suffixes: p = pico = 10-12 n = nano = 10-9 u = micro = 10-6 m = milli = 10-3 k = kilo = 103 meg = mega = 106 Using these keeps your schematic looking neat, especially for larger projects. 15. Attach one end of the voltage source to the end of the resistor, and the other end to a new ground part. Your schematic should look like this: Figure 8. The op amp with the voltage source attached 16. Before the amplifier can be simulated, it must also have power. The power supply you created at the beginning will be used. One of the problems with creating schematics is that they will start to look messy if long wires are placed all over the schematic. In order to avoid this, a net alias can be created. A net alias gives a name to a certain node. Whenever you place another net alias with the same name at another node, it will connect the two together, without using a wire. To create a net alias, click Place Net Alias in the menu or on the tool bar. Give it the name ‘V+’, and click ok. A net alias can only be placed on a wire. Place the V+ above the wire of the +9 Volts on your power supply. Similarly, create a net alias named ‘V-‘, and place it above the wire for the -9 Volt power supply. Figure 9. The power supply with net aliases 17. Now, create two wires out of each power terminal on the op amp. Create two new net aliases with exactly the same name as those connected to the power supply. Place the ‘V+’ alias as the positive power terminal, and the ‘V-‘ pin at the negative power terminal. Using Plots in PSpice 18. The next step is to check if the amplifier is working. This time, however, PSpice will be used to provide a graph of Voltage vs. Time at the output and input. On the top tool bar, select the Voltage Level Marker. Place a marker at the output node of the op amp and the output of the VSIN part. Figure 10. The voltage marker button