Cadence PSpice Tutorial Basics (reprint)

First, the PSpice work flow

Second, PSpice A/D basic analysis content

The schematic diagram of the circuit needs to be drawn before the analysis method is selected, and the OrCAD Unified by the Capture window for input and call PSpice analysis. Where the schematic diagram should be drawn when using PSpice.

1, new Project should choose Analog or mixed-signal circuit

2. The device to be called must have a PSpice model

First, call the model library provided by the OrCAD software itself, which stores the path to Capture\library\pspice, and all the devices in this path have a pspice model that can be called directly.

Second, if you use your own device, you must ensure that *.olb, *.lib two files exist simultaneously, and that the device attribute must contain the PSpice Template attribute.

3, the schematic diagram must have at least one network name of 0, that is, grounding.

4, must have an incentive source.

The port symbol in the schematic does not have power characteristics, and all the excitation sources are stored in the source and Sourcetm libraries.

5, the power supply is not allowed to short-circuit, not allowed only by the power supply and inductance to form a circuit, also does not allow only a cut set of power and capacitance.

Solution: Capacitance in parallel a large resistor, inductance series a small resistor.

6, it is best not to use negative resistance, capacitance and inductance, because they tend to cause non-convergence.

The next step is to introduce several basic analysis methods and parameter settings.

1, DC analysis (DC sweep)

DC analysis refers to the circuit of a component parameter as an independent variable within a certain range, to each value of the independent variable, the output of the circuit to calculate the DC bias characteristics of the variable. This procedure can also specify a parameter variable, and determine the range of values, each setting the value of a parameter variable, the output variable is calculated with the characteristics of the independent variable. DC Analysis is also the analysis required to determine the initial values of the small signal linear model parameters and transient analysis when communicating the analysis. After the simulation, the Probe function can be used to plot the Vo-vi curve, or the transmission characteristic curve of any output variable relative to any component parameter.

First we turn on Cadence/release 16.5/orcad Capture CIS and open the interface shown in 1-1.

Next use the menu: Start File/new/poject to build a new project, shown in 1-2.

In the Figure 1-3 dialog box, enter a file name, such as "RC". Select "Analog or Mixed A/D project" in the radio button below, and be aware that this is a button called PSpice by Capture directly, so don't choose the wrong one. So what do the other options mean?

Analog or Mixed A/D digital-to-analog hybrid simulation

PC Board Wizard system level schematic design

Programmable Logic Wizard CPLD or FPGA design

Design of Schematic schematic diagram

Finally, after pointing to the folder in location, click OK and the Figure 1-4 screen appears.

You can see many existing engineering and circuit diagrams under "Create based upon an existing project". We selected "Create a Blank Project", entered into the Simulation Diagram drawing window and began to draw the circuit diagram. As shown in 1-5.

Next, we have to learn to select the device: Select the Drawing toolbar, click on the following Figure 1-5 window appears to place the component window as shown in Figure 1-6. Note that the selected device library must be stored in the path to Capture\library\pspice, and all devices in this path have a pspice model that can be called directly. Live if you are using your own device, you must ensure that *.olb, *.lib two files exist simultaneously, and that the device attribute must contain the PSpice Template attribute, which is the tag required for the device selected in the Figure 6 dialog box. (For new devices, there is a special tutorial to explain later)

1-6, we choose to enter "R", find the resistor under the Analog.lib, double-click it can be placed in the drawing window.

Let's take a simple example to get a look at the engineering of simulation. Of course, the first is DC Scan analysis (DC Sweep)
In the schematic drawing window of Figure 1-5, enter the circuit shown in 1-7.

Device information used:

The circuit diagram is ready to save, and then you start to set the simulation parameters to start simulation. First, create a new simulation file, launch the pspice/new Simulation command, or click directly on the Emulation toolbar
button to get the dialog box shown in Figure 1-8. Enter the simulation file name in the name, such as: DC, click "Create", in the original project folder will automatically generate a folder called "DC", the results of the simulation and the project are saved in the folder, the party is easy to manage.


Figure 1-8 Simulation Parameter Settings dialog box

When you finish figure 1-8, the simulation parameter Settings window shown in Figure 1-9 pops up. Let's start with the analysis.

In analysis type, we select the DC Sweep.
In Option, we select Primary Sweep.
The following options can be seen in Sweep variable:

Voltage Source voltage Source information

Current source information

Global parameter parameters

Model parameter parameter

Temperature temperature setting

In the Sweep type, we can set to Linear (linear); Logarithmic (logarithmic), Value Line (set point). Here we set the voltage source V1, the scan value is -6v to 10V, each increment 1V.
When set, click OK. Then click on the Simulation toolbar to run the simulation. The PSpice interface is then paged out, as shown in 1-10.

The main toolbar in the PSpice interface has the meaning 1-11 shown.

Select the menu bar Trace/add Trace, or click on the icon to get the Figure 1-12 dialog box, where we can see there are two tabs Simulation Output variables with Functions and Macros. "Simulation Output variables" contains many variables, and "Functions and Macros" have information functions that need to be measured. In the process of operation, for example, to see the maximum value, first select the Max () function, and then select the variable type V1 (D1). We can see the expression in Trace expression: MAX (V1 (D1)). This is one of the most basic steps. If the output V2 (D1) is selected, the waveform of Figure 1-13 is obtained. Waveforms can be used to analyze whether the design requirements are met.

2. AC analysis (ac Sweep)
The function of AC analysis is to calculate the frequency response characteristic of the AC small signal of the circuit. : The PSpice can perform AC analysis on small-signal linear electronic circuits, at which time the linear model is used for the semiconductor devices. It is based on the analysis of the performance of the circuit due to the change of signal frequency, it can obtain the amplitude-frequency response and phase frequency response of the circuit, as well as the transfer admittance and other characteristic parameters.
As in front, we created a new project BANDPASS.OPJ. The preceding drawing schematic and the new simulation file operate in the same way as DC analysis. This is shown in schematic 1-13.

Next, make the following settings for Simulation Setting:

Figure 1-14 Sets the frequency from 1Hz to 100MHz, note that the PSpice is not in the case of the English letter, so it is indicated by Meg (m), but not by M, because M stands for No. Figure 1-14 After clicking OK, also click on the Simulation toolbar
, run the simulation. This brings up the PSpice interface, select the menu bar Trace/add Trace, or click the icon, select DB () in Functions and Macros, and then locate "V" in Simulation Output variables (ou T) "To get the amplitude-frequency characteristics of the output waveform of Figure 1-15 in the decibel representation of the baud graph.



Click Plot/add y axis, add a Y axis, then select the menu bar Trace/add Trace, or click the icon, select P () in Functions and Macros, and then in the Simulation Output variables "V (out)" to obtain the output waveform of Figure 1-16 amplitude and phase-frequency characteristics of the graph.


If you need to calculate the bandwidth and upper and lower frequencies of the bandpass filter, you can call the feature function, select the icon, pop up the figure 1-17 interface, select Bandwidth (1,db_lever), 1 in parentheses represent the input variable, so in simulation Output vaiables Select V (out), and then enter 3 to display Bandwidth (V (out), 3) in the "Trace" expeession. When you click OK, the value of 3dB bandwidth is displayed under the Waveform display window. The upper and lower frequencies can also be calculated, as shown in result 1-18.

The functions of some of the functions in Figure 1-17 are described below

After the waveform display we can also use the Toggle cursor tool to measure, click on the small icon, we can see the back of the toolbar from the Gray lock state into a usable state. At the same time, there will be more data in the lower corner of the information box, the contents of the information box can be copied to Word or Excel.

Let's start by introducing the effect of the toolbar that becomes available:

For the circuit in Figure 1-13, you can label the upper and lower frequency values in the diagram, as shown in 1-19.

3. Transient analysis (Time Domain (Transient))

The purpose of transient analysis is to calculate the transient response at the output of the circuit under the action of a given input excitation signal. When the transient analysis is performed, the initial state of the circuit is calculated first, and then a certain time step is selected from t=0 to a given time range to calculate the output level of the output at different t=0. The transient analysis results are automatically deposited in a data file with the. dat extension, which can be used to analyze the signal waveform showing the simulation results using the Probe module. Transient analysis uses the most, the most complex, and is the most expensive part of computer resources.
A first-order RC differential circuit is used for analysis, and a schematic diagram 1-20 is drawn in capture.

First explain the meaning of several parameters of the pulse signal source (Vpulse)

Note: The Tstop in the table is the set value of the Final time of the parameter in the transient analysis, and the tstep is the setting value of the parameter Print Step.
Now let's set Simulation Setting, in the settings Simulation Setting, the analysis Type option is selected for Time Domain (Transient). Set parameter 1-21 as shown.

Click OK, and then click on the Simulation toolbar to run the simulation. This brings up the PSpice interface, select the menu bar Trace/add Trace, or click on the icon, "Simulation output variables" to find "V (r1:2)", the output waveform, also can be plot/add The Plot to window increments the window to display the input waveform. As shown in 1-22.


It is also possible to observe waveform changes by modifying the resistor or capacitance value. For example, the modified capacitance value of 1u, can be found that the output waveform pulse signal significantly changed. The reason is that the RC time constant is shorter, of course, the pulse signal is sharp. An easier way to observe the effect of a component on the final waveform in a circuit is to scan the parameters that we will describe in tutorial two.

If you need to compare the results of two analyses, you can do this by saving the waveform at c1=10uf (such as 10u.dat), then modifying the component parameters in the schematic, running the simulation, and getting the results, as shown in File/appeng waveform (. dat) 1-24.

In the pop-up selection file dialog box, locate the 10u.dat file that you just saved so you can compare the changes in the waveform before and after the change, as shown in 1-25.

4. Static work point analysis (Biaspoints)
Static work point analysis refers to the calculation of the static working point of the circuit by using the iterative method to calculate the DC level value of each signal source in the case of inductance short circuit and capacitance open circuit. The analysis results include the voltage of each node, the current flowing through each voltage source, the total power consumption of the circuit, the bias voltage of the transistor and the current of each pole and the parameters of the small signal linearization model under this operating point. The results are automatically stored in the. Out output file. In electronic circuits, it is important to determine the static operating point, because it can determine the small signal linearization parameter value of the semiconductor transistor. Especially in the amplification circuit, the static working point of the transistor directly affects the various dynamic indicators of the amplifier. So we take a small signal amplification circuit as an example to illustrate the use of the analysis method and simulation results. As in front, we created a new project AMP.OPJ. The procedure for drawing a schematic and creating a new simulation file is the same as for DC analysis. This is shown in schematic 1-26.

Next, make the following settings for Simulation Setting:

Click OK, and then click on the Simulation toolbar to run the simulation. This brings up the PSpice interface. By selecting View/output file, 1-28, you can open files that store the static work point simulation results. 1-29, the amplifier determines the static operating point of the main observation transistor VCEQ,IBQ and ICQ three values, the appropriate static operating point needs to be located in the transistor output characteristic curve of the amplification area, preferably close to the middle of the AC load line.

If the option to include the DC sensitivity analysis in Figure 1-27 is hooked and a VCE (Q_Q 1) is entered on the output variable, it is necessary to analyze the sensitivity value of the static output resistance of a component in the circuit to the transistor. The results are also recalled in the. out file. As shown in 1-30. The elements in the red box have a greater effect on the static VCE of the transistor.

Conclusion: PSpice the most basic functions can be so perfect circuit simulation, feeling today's EDA software. It's a great tool to reduce the time we have to debug the circuit and to do our own design with a little slack. Immediately we will PSpice further analysis methods to introduce, I believe slowly you will and I like this software, and then inseparable from this software.
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Cadence PSpice Tutorial Basics (reprint)