Spice simulation tutorial pdf

A Virtual Lab on Your Desktop! More content by David Haboud. Recent Articles. Read Article. Do you know when a power plane resonance occurs in the PDN on a circuit board? What is Spreading Inductance? The spreading inductance of a plane pair has a simple meaning, but it can be difficult to calculate. Here are some points designers should know about the spreading inductance of a plane pair.

We aim to give you the knowledge you need to design a manufacturable PCB confidently. Download PDF. Watch or listen on the go and learn the critical components for an effective process to achieve high-reliability PCB design. Mname refers to the switch model that is defined in another statement see Model Statement below. In case of a switch, we have:. Dname is the device name: Vswitch or Iswitch.

Operational Amplifiers, and other elements An operational amplifier can be simulated in different ways. The first method is to model the amplifier by resistors, capacitors and dependent sources.

As an example an ideal opamp is easily simulated using a voltage dependent voltage source. The second option uses actual transistors to model the opamp. The device library contains nonlinear models of the most common op amps.

LIB file. The professional version comes with library files of many commercial amplifiers and devices. An example of the first approach linear AC model is given below for the uA opamp. We defined a subcircuit for the opamp. Subcircuits A subcircuit allows you to define a collection of elements as a subcircuit e.

Defining a subcircuit A subcircuit is defined bu a. Element statements. The external nodes cannot be 0. The node numbers used inside the subcircuit are stricktly local, except for node 0 which is always global.

For an example, see Operational Amplifier above. Using a subcircuit The element statement for a subcircuit is similar to any other element. The format is as follows: Xname N1 N2 N An example of an inverting opamp circuit using the subcircuit of the the uA see operational amplifiers above is given below. The subcircuit is called x1. Semiconductor Devices Most of the elements that have been described above require only a few parameters to specify its electrical characteristics.

However, the models for semiconductor devices require many parameter values. A set of device model parameters is defined in a separate. MODEL statement and assigned a unique name. This method alliaviates the need to specify all of the model parameters on each device element card. Thus a semiconductor device is specified by two command lines: an element and model statement.

The syntax for the model statement is:. If a parameter is not specified the default value given in parenthesis is assumed. As an example, the model parameters for a 1N commercial diode are as follows:. For a complete list of the parameters please refer to one of the references. A circuit example with a npn transistor can be found under the section Examples m3. ModName is the name of the transistor model see further.

L and W is the length and width of the gate in m. The above paramters are usually sufficient when specifying discrete transistors. However, for integrated circuit simulations one need to specify several other parameter values related to the transistor geomtry. These are optional. PD and PS are the value in m of the perimeter of the source and drain.

NRD is the number of squares of the drain diffusion for resistance calculations. TRAN card, when a transient analysis is desired starting from other than the quiescent operating point.

See the. IC card for a better and more convenient way to specify transient initial conditions. Model statement:. There are several other transistor parameters that can be specified, in particular when doing simulations of integrated circuits. The general form of the. MODEL statement is as follows:. However to simulate integrated circuit transistors, one need to use a more sophisticated models.

Refer to the references for a complete list of parameters. An example of the model parameters of the 1. ModName is the name of the transistor model Model statement:. OP Statement This statement instructs Spice to compute the DC operating points: voltage at the nodes current in each voltage source operating point for each element In PSpice it is usually not necessary to specify. OP as it gives you automatically the DC node voltages.

However, HSpice does not give the DC voltages unless you have specified a certain analysis type, such as for instance. TRAN, or. Thus, if you are only interested in the DC voltages in HSpice, you should specify the. OP option, or the. DC option see further.

DC Statement This statement allows you to increment sweep an independent source over a certain range with a specified step. The format is as follows:. DC command produces only one value. This may be usefull in HSpice when you do not want all the DC voltages and currents to be printed with the. OP option , but are interested in a limited number of DC voltages and currents. In the. PRINT statement see further you would then also specify the node voltages you like to know ex.

You can nest the DC sweep command which is often used to plot transistor characteristics, such as the Drain current ids versus the Drain-source voltage Vds for different gate voltages Vgs. This can be done as follows:.

TF Statement The. TF statement instructs PSpice to calculate the following small signal characteristics: the ratio of output variable to input variable gain or tranfer gain the resistance with respect to the input source the resistance with respect to the output terminals.

TF statement can be used to find the Thevenin small signal equivalent resistance. The Thevenin voltage is given by the node voltage at the open circuit terminal, as a result of the.