Programming instructions

Capacitor
 National Instruments Corporation 2-21 Multisim Component Reference Guide
2.7.1 Characteristic Equation
The current through the capacitor is equal to C multiplied by the rate of change in voltage
across the capacitor, that is:
2.7.2 DC Model
In the DC model, the capacitor is represented by an open circuit.
2.7.3 Time-Domain Model
R
cn
is an equivalent resistance and i
cn
is an equivalent current source. The expression for the R
cn
and
i
cn
depends on the numerical integration method used.
For trapezoid method:
For the first-order Gear method Backward Euler:
where:
V
n+1
= present unknown voltage across the capacitor
i
n+1
= present unknown current through the capacitor
V
n
, i
n
= previous solution values
h = time step
n = time interval
iC
dv
dt
=
R
h
C
i
C
h
Vi
cn
cn n n
=
=+
2
2
R
h
C
i
C
h
V
cn
cn n
=
=
ComponentRef.book Page 21 Thursday, December 7, 2006 10:12 AM