Getting Started with OrCAD 9.2
This article contains the material I prepared for a presentation I have done at my university. Thorough out this post I will discuss to draw schematic, simulate in time domain and frequency domain and design the PCB for a simple transistor amplifier with covering some of mostly used topics in OrCAD.
Let’s start with the transistor amplifier circuit. Potential Divider biased Class A amplifier. Calculate IB, IC, VCE and VC of following circuit. Take β = 100.
Now lets simulate this circuit on OrCAD.
1. Go to Start Menu -> Orcad Family Release 9.2 -> Capture CIS (Or Capture).
2. Now you have to create a project to continue.
a. Go to File -> New –> Project
b. Select Project Type as Analog and Mixed A/D, set a location for your project, make sure the location name does not contain any spaces (for best practices). Set a Project Name and Click OK to continue.
c. In next window select ‘Create Blank Project’ and click OK
3. Now in the OrCAD Capture window you can see three sub windows opened, Schematic, Session log and Project Overview.
4. If you expand your project overview, you can see a special icon in SCHEMATIC1 node, (like this) it implies that the PAGE1 schematic will work as the ROOT of the project, and anything we perform will apply for the schematics related (based) to the schematics in ROOT.
5. Now Lets start drawing our schematics. As the first step you have to add libraries for the project. To add libraries, follow these steps.
a. Click on Place -> Part or press ‘P’ as the short cut, Now click on Add Libraries
b. Browse the folder <C:\Program Files\Orcad\Capture\Library\PSpice>
c. Add all existing files in there.
d. Press ESC to close the ‘Place Part’ window
6. Lets start placing resistors and capacitors.
b. There are two icons below the Symbol of the resistor. First icon means the model you selected have the PSPICE model for simulation and second says you have the model for Layout (that is PCB Design) for the selected.
Now Click OK and place 4 resistors in your schematic. Press ESC to exit.
c. Continue the same procedure by pressing ‘P’ and ‘C’ to place capacitor. Place 3 Capacitors.
7. Now you have to place the transistor. There are several variations of BC109, so lets filter them first and select one of them. Press ‘P’ to open Place part window and type *BC109* and press Enter. This will filter all the devices which contains the text BC109. Lets Select BC109C/E and place it on the schematic window.
8. Now place the componets in order and connect them using the wire. (To activate the wire, press W) To rotate components, select the component and press ‘R’. Or right click on a component and you will find its option menu.
9. Now place the components and connect them. And update the values of the resistors and capacitors by double clicking on their values.
10. Now for the simulations you have to add several components, they are Signal Source, Power and Ground and a Load.
a. Press G to activate ground connector and Place it in the 0v line of the circuit. This GND connection is very important, since without it OrCAD identifies the system as floating and simulation cannot be done.
b. Then Place VDC from Place Part window as the power input and set its voltage as 6V.
c. Place 1k load to the output of the amplifier.
d. Place Vsin as the signal input to the system. Set Frequency as 1KHz and amplitude as 100mV.
e. Final circuit will be as follows.
Simulations – Time Domain
1. Click on PSpice from the Menu and select new simulation profile. Enter a name and click Create to create the profile.
2. It will initial PSPICE and open the simulation settings window. We will first do a time domain simulation and later we will do a simulation in frequency domain. Set the analysis type as Time Domain (Transient) and Run to Time as 0.02 seconds. And click OK.
4. Now get the Voltage Level marker from PSpice->Markers and connect them to the input and output of the amplifier.
You can notice that the phase difference between the input and output signal is not 180 degrees. Which means this 1000Hz point is in the transition band of the amplifier. So what is the frequency band which this amplifier can amplify well?
In order to identify the frequency response of this amplifier, we can perform a AC Sweep simulation and later we can adjust the coupling capacitors so that the amplifier will be in the correct band.
Simulations – Frequency Domain
To proceed to next step make sure you have saved your current design.
1. Open the file hierarchy and right click on .\bjtamp.dsn and click new schematic. Then Right click on new schematic and select new page.
2. Then right click on the new schematic again and select Make root. Now all the analysis will be based on the circuits you draw in your new schematic page. Again save once before making root.
3. Now copy your old circuit from previous schematic and paste it on the new schematic page.
Remove Vsin source and replace it win Vac source. Now your new schematic should be like this.
4. Now create a new simulation profile and set its parameters as below.
5. Click OK and goto PSPICE -> Markers -> Advanced -> dB Magnitude of Voltage and place it in the output of the amplifier. Now Run the simulation again.
6. It seems to be performing well at the high frequencies, Now lets make some changes in the capacitors and run the simulation again. Now change all the capacitor values into 100uF, R2 as 22k and re-run the simulation.
Switching between schematics and simulation profiles.
Now we can see that the Frequency response is in a good shape and it will be able to properly amplify our 1kHz input signal. Now lets do the same change in our time domain circuit and see the observation.
1. Save all the changes, go to the file explorer window and make the schematic1 as the root again.
2. Now under the PSpice Resources -> Simulation Profiles, right click on the simulation profile of schematic 1 and click make active
3. Now open the schematic and perform the changes we made after the frequency domain analysis. That is making all the capacitor values into 100uF. And set the input amplitude as 10mV.
4. Now run the simulation
You will be able to observe the run distorted output signal with 180 phase shift.
Schematic to PCB
Now for the PCB we will replace the Signal source, Load and Power source by connectors. Follow the same procedure, create a new schematic and paste the circuit you have simulated. Make it ROOT.
Now you have to add connectors. First you have to add the connector library. Go to place part window, select add library and from one level up from the PSpice folder, you can locate the Connectors.olb file and add it.
Now for the Signal input and outputs place 2 BNC connectors. For power, place CON2 connector. Note that the both BNZ and CON2 do not have footprints associated with. Let’s ignore this for the moment.
Now your new schematic will be like this.
Now go to the file explorer, click on your schematic name, and then go to Tools->Create NetList. Now netlist options window will be open. Under the layout tab it will notify where the MNL file is located. Click OK to continue.
Check session log to validate the process.
Now go to the start menu. Go thorugh Orcad Family Release 9.2 and click on Layout Plus.
Go to File -> New, It prompt to select the Technology file. Select _DEFAULT.TCH file from the location [C:\Program Files\Orcad\Layout_Plus\Data].
Then It will prompt to select the *.mnl file, (NetList source). Select the *.mnl file created in previous step.
Now System will prompt to save the *.max file which is the PCB design. Set the location and click save to continue.
Since we have not added any footprints to BNZ or CON2 a message window will pop up and prompt to assign foot prints.
Select Link existing foot print. Set Jumper400 under Jumper library as the footprint.
For BNZ connector, set RF/BNC/R1.350 under RF library.
Now Layout Plus window will open with the components. First go to Tools, Layer and Select from Spread Sheet.
Since we are only using the bottom layer as the routing layer, set other four layers as unused routing layers and close the spread sheet.
Under System Settings in Options, set the grid according to your preferences.
Now select the component tool from tools menu and place the components.
After Placing the components, draw the border outline using obstacle tool.
For PCB routing, first setup layer clearances by Options -> Global Spacing. Modify the spread sheet according to your requirements and close it.
Now click on Add/Edit Segment and start routing by clicking on connections. You can set the width of the tracks by pressing ‘w’ while the route is in progress.
I am planning to add a copper pour as the ground
Now to add the copper pour, select the obstacle tool, set its type as Copper Pour. And draw the polygon shape you want to fill up. Set the copper pour settings as follows.
Now that’s it, your PCB is ready for fabrication.
Final step is to create the Gerber files to send to the PCB manufacturer.
Go to Tools -> Run post processor.
Then your Gerber files will be created in your project folder.
Hope you got a basic idea how to work with OrCAD. Thank you very much for reading.