Cadence PSPICE SCHEMATIC Uživatelský manuál stáhnout pdf (Strana 18)

Figure 24: Simulation settings for a parametric sweep alone. The Analysis type is DC sweep.

An obvious question is: Which curve goes with which parameter? There seems to be no

way of displaying a legend. The simplest way is to double-click on one of the symbols below

the plot. This brings up a box with information about the simulation, including the value of the

parameter.

3.7 Parametric sweep only

In the previous simulation we performed a DC sweep for each value of the parameter. In fact

the DC sweep is pointless because it just gives a straight line. We could instead plot the voltage

as a function of Rload, keeping V1 constant at its original value of 10 V. In other words, we

vary the parameter alone. This isn’t done very often but is appropriate here. Figure 24 shows a

suitable simulation proﬁle. It is set up as a DC sweep although we do not sweep either a current

or voltage. It looks rather like ﬁgure 22 on page 16 except that the parameter is used for the

primary sweep, not the parametric sweep.

Figure 25 on the following page shows how the voltage depends on Rload. The curve would

be smoother if more points were requested by reducing the increment in ﬁgure 24.

Modify the plot to show the power dissipated in the load resistor, rather than the voltage

across it. This is most easily done with the probes in Capture. What value of Rload gives the

maximum power dissipation? You may need to run the simulation with more points to get an

accurate value. Does the result agree with theory?

4 Frequency response of an RC circuit

We’ll now use Spice to analyse the behaviour of a simple circuit as a function of frequency.

This is the RC ﬁlter shown in ﬁgure 26 on page 20. A ﬁlter is typically used to remove cer-

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Cadence PSPICE SCHEMATIC Uživatelský manuál Strana 18