User`s guide

PSpice A/D-Equivalent Parts 6
-31
be either the voltage at a net, such as V(5), or the voltage across
two nets, such as V(4,5). Currents must be the current through a
voltage source (V device), for example, I(VSENSE). Voltage
sources with a value of 0 are handy for sensing current for use
in these expressions.
Functions may be used in expressions, along with arithmetic
operators (+, -, *, and /) and parentheses. Available built-in
functions are summarized in Table 3-2 on page 3-18
.
The EVALUE and GVALUE symbols are defined, in part, by
the following attributes (default values are shown):
EVALUE
EXPR V(%IN+, %IN-)
GVALUE
EXPR V(%IN+, %IN-)
Sources are controlled by expressions which may contain
voltages, currents, or both. The following examples illustrate
customized EVALUE and GVALUE parts.
Example 1
In the example of an EVALUE device shown in Figure 6-15, the
output voltage is set to 5 volts times the square root of the
voltage between pins %IN+ and %IN-.
The attribute settings for this device are as follows:
EXPR = 5v * SQRT(V(%IN+,%IN-))
Example 2
Consider the device in Figure 6-16. This device could be used as
an oscillator for a PSK (Phase Shift Keyed) modulator.
A current through a source is a sine wave with an amplitude of
15 mA and a frequency of 10 kHz. The voltage at the input pin
can shift the phase by 1 radian/volt. Note the use of the TIME
parameter in this expression. This is the PSpice A/D internal
sweep variable used in transient analyses. For any analysis other
than transient, TIME = 0. The relevant attribute settings for this
device are shown below:
EXPR = 15ma*SIN(6.28*10kHz*TIME+V(%IN+,%IN-))
Fi
g
ure 6-15
EVALUE Part
Example
Fi
g
ure 6-16
GVALUE Part
Example