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40 2. Tutorial
Controlled Sources: Some Caveats
If you have worked with SPICE netlists before you will see some differences in the way you have
to formulate the netlist entries for controlled sources in an Analog Insydes netlist. Apart from the
more meaningful type tags (VV, CC, VC, CV as opposed to E, F, G, H), Analog Insydes uses a uniform
scheme for all four types of controlled sources, i.e. you have to specify two nodes for the controlling
branch and two nodes for the controlled branch for both voltage-controlled and current-controlled
sources.
C1
N1
1
3
I1
r*I1
V1
gm*V1
C2
N2
2 4
Figure 2.5: Current-controlled voltage source (left) and voltage-controlled current source (right)
For the two controlled sources shown in Figure 2.5 the netlist entries must be written as follows.
Note, that the nodes of the controlling branches are listed first.
{CV1, {C1, C2, N1, N2}, r}
{VC2, {1, 2, 3, 4}, gm}
Analog Insydes treats controlled sources as true two-port elements, so every controlled source adds
two electrical branches to a circuit, a controlling and a controlled branch. In the case of currentcontrolled
sources you have to keep in mind that the controlling branch is nothing else than a short
circuit (Section 4.2.8). Therefore, do not connect the controlling branch of a current-controlled source
in parallel to another circuit element. Instead, always use a series connection of the controlling
branch and the circuit element whose branch current controls the source.
Let’s clarify this important point by writing a netlist for the circuit shown in Figure 2.6. The currentcontrolled
current source is controlled by the current flowing through the resistor RB. If we wrote
the netlist entry for the CCCS (Section 4.2.11) as
{CC1, {1, 0, 2, 0}, beta}
the controlling branch would be inserted in parallel to RB and thus short-circuit the resistor.