The Constant Current Source:
What is it?
It is a two terminal electrical component that generates a
constant current (charge flow).
A Voltage Controlled Current Source (VCCS) can also be used
as a constant current source, however the Constant Current Source
is easier to set up and requires less schematic area.
What is it good for?
A constant current can be used to model a fixed income or expense.
Tell me more!
At the left is shown a one amp constant current source driving a one
farad capacitor. This could model a savings of $1K per month into
a bank account. The starting voltage on the capacitor is set to zero
using the initial condition (I.C.) component. The test point TPv1 monitors the
voltage versus time at the capacitor. In this circuit the top of the capacitor
connects to node 1 and the bottom connects to node 0 (ground).
SPICE description format for this circuit is:
I1 0 1 1.0
C1 1 0 1.0
The simulation result is:
Note that the resulting voltage on the capacitor increases linearly
with time. Recall from the Capacitor component that CV=Q. Since the
charge, Q, flowing into the capacitor is equal to IT (current*time), we can know CV=IT.
Since C and I are constant in this equation, the voltage is proportional to time.
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