Cadence PSPICE SCHEMATIC Manuel d'utilisateur télécharger pdf (Page 19)

Figure 25: Plot of voltage as a function of Rload.

tain frequencies from a signal or pick out a frequency of interest. For example, a low-pass

ﬁlter allows signals with low frequency to pass unaffected but attenuates (makes weaker) high-

frequency signals. This might be used to remove high-frequency noise from a signal that is

known to vary slowly – the temperature of a room, for instance.

First, analyse the behaviour of this circuit by hand (assuming that you have done this in the

lectures). Follow these three steps.

1. What are the limiting forms of the impedance of the capacitor at high and low frequency?

2. From these, work out the behaviour of the ﬁlter at high and low frequency. Is it a high-

pass or low-pass ﬁlter?

3. What is its half-power, −3dB or Bode frequency, which separates ‘low’ and ‘high’ fre-

quencies?

Now simulate the ﬁlter. Create a new project in Capture (remember to make a new directory

ﬁrst) and draw this circuit.

• The source is a VAC and is in the source library. I changed its name from V1 to Vin,

which is more descriptive. Leave the voltages at their default values.

• The symbol on the right is an off-page connector. This is really intended for carrying

signals from one page of a large drawing to another but is a clear way of naming signals

on the circuit. You can ﬁnd it on the Place menu or use the button.

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Cadence PSPICE SCHEMATIC Manuel d'utilisateur Page 19