Download - Wolfram Research

388 3. Reference Manual
Define an AC model for
BJTs.
This netlist describes a
common-emitter amplifier.
Set up a system of
symbolic AC equations.
Compute the complexity
estimate.
In[2]:= Circuit[
Model[
Name −> BJT,
Selector −> AC,
Scope −> Global,
Ports −> {B, C, E},
Parameters −> {Rbe, Cbc, Cbe, beta, Ro,
RBE, CBC, CBE, BETA, RO},
Definition −> Netlist[
{CBE, {B, E}, Symbolic −> Cbe, Value −> CBE},
{RBE, {X, E}, Symbolic −> Rbe, Value −> RBE},
{CBC, {B, C}, Symbolic −> Cbc, Value −> CBC},
{CC, {B, X, C, E},
Symbolic −> beta, Value −> BETA},
{RO, {C, E}, Symbolic −> Ro, Value −> RO}
]
]
] // ExpandSubcircuits;
In[3]:= ceamplifier =
Circuit[
Netlist[
{V1, {1, 0}, 1},
{V0, {6, 0}, 0},
{C1, {1, 2}, Symbolic −> C1, Value −> 1.0*^−7},
{R1, {2, 6}, Symbolic −> R1, Value −> 1.0*^5},
{R2, {2, 0}, Symbolic −> R2, Value −> 47000.},
{RC, {6, 3}, Symbolic −> RC, Value −> 2200.},
{RE, {4, 0}, Symbolic −> RE, Value −> 1000.},
{C2, {3, 5}, Symbolic −> C2, Value −> 1.0*^−6},
{RL, {5, 0}, Symbolic −> RL, Value −> 47000.},
{Q1, {2 −> B, 3 −> C, 4 −> E},
Model −> BJT, Selector −> AC,
CBE −> 30.*^−12, CBC −> 5.*^−12, RBE −> 1000.,
RO −> 10000., BETA −> 200.}
]
]
Out[3]= Circuit
In[4]:= eqs = CircuitEquations[ceamplifier,
ElementValues −> Symbolic]
Out[4]= DAEAC, 10 10
In[5]:= ComplexityEstimate[eqs]
Out[5]= 132
The number returned by ComplexityEstimate indicates that solving the equations for any transfer
function is feasible, but the result cannot be expected to yield much insight into circuit behavior.