Behavioral Source (bsource)

Behavioral source enables you to model a resistor, inductor, capacitor, voltage or current source as a behavioral component. Using bsource, you can express the value of a resistance, capacitance, voltage or current as a combination of device operating points, node voltages, branch currents, and built in Spectre^® circuit simulator expressions. bsource simulation performance has now been improved by compiling the bsource devices.

Bsource simulation performance has been improved by compiling the bsource devices. This is explained in more detail in the bsource compilation section below.

Sample Instance Statement

name (node1 node2) bsource behav_param param_list 

where behav_param can be

c=simple_expr	Capacitance between the nodes
g=simple_expr	Conductance between the nodes
i=generic_expr	Current through bsource
l=simple_expr	Inductance between the nodes
phi=simple_expr	Flux in the bsource device
q=simple_expr	Charge in bsource device
r=simple_expr	Resistance between the nodes
v=generic_expr	Voltage across the nodes

A simple_expr is defined as a spectre expression containing,

1. netlist parameters
2. current simulation time, $time
3. node voltages, v(a,b), where a and b are nodes in the spectre netlist or v(a), which is voltage between node a and ground
4. branch currents, i("inst_id:index"), where inst_id is an instance name given in the netlist and index is the port index. The default value for index is 0.

A generic_expr is defined as a simple_expr or ddt() or idt() of simple_expr. The param_list is param_name=value.

Multiplicity factor

m	The value of m will be default to1.

Temperature Parameters

tc1	Linear temperature co-efficient. Valid for all behavioral elements. Default value is 0 1/C.
tc2	Quadratic temperature co-efficient. Valid for all behavioral elements. Default value is 0 C^-2
tnom	Parameters measurement temperature. Valid for all behavioral elements. Default value is 27.0.
trise	Temperature rise for ambient. Valid for all behavioral elements. Default value is 0.0.
T	Effective value of temperature. Valid for all behaviroal elements. Default value is temp+trise-tnom.
tc1c	Linear temperature coefficient of capacitor. valid for transistor type behavioral element. Default is 0 1/C
tc2c	Quadratic temperature coefficient of capacitor. valid for transistor type behavioral element. Default is 0 C-2

Clipping Parameters

max_val	Maximum value of bsource expression. Valid for all behavioral elements, but mostly used with i and v elements for clipping the current or voltage between the specified values.
min_val	Minimum value of bsource expression. Valid for all behavioral elements, but mostly used with i and v elements for clipping the current or voltage between the specified values.
bv_max	Generate a warning when bsource voltage of two terminals exceeds the value specified by bv_max.

Noise Parameters

af	Flicker noise exponent, Valid for r and g elements Default value is 2.
fexp	Flicker noise frequency exponent. Valid for r, g, v, and i elements. Default value is 1.
ef	Alias of fexp.
ldexp	Flicker (1/f) noise L component. Valid for r and g elements. Default value is 1.0.
lf	Alias of ldexp.
wdexp	Flicker (1/f) noise W component. Valid for r and g elements. Default value is 1.0.
wf	Alias of wdexp.
isnoisy	Specifies whether to generate noise. Valid for r, g, i, and v elements Valid values are yes and no. Default value is yes.
kf	Flicker noise co-efficient. Valid for r and g elements.
white_noise	White noise expression. Valid for v and i elements.
flicker_noise	Flicker noise expression. Valid for v and i elements.

DC Mismatch Parameters

mr	DC-Mismatch parameter. Valid only for r.

Other Parameters

scale/scaleb/scaler/scalei/scalec

Bsource scaling factor. Default value is 1.0.

ctype

Different implementations of a capacitor. When the value is 1, bsource current is ddt(cap*V(node1, node2)), where cap is the bsource capacitor value with temp effect, mfactor effect, scale effect and so on. V(node1, node2) is the voltage between the bsource terminals. When the value is 2, the current is ddt(cap). When the value is 0, or any other value, the current value is cap*ddt(V(node1, node2)).

Instance Parameters

bsource supports the following instance parameters for the Spectre primitives.

Resistor	isnoisy, m, r, tc1, tc2, trise, kf, af, fexp, ldexp, wdexp, l, w, mr.
Capacitor	c, m, tc1, tc2, trise, ic.
Inductor	l, m, tc1, tc2, trise.

Related Topics

Mathematical Definitions

Noise Model for bsource

Circuit Components

Mathematical Definitions

The i and v elements are current and voltage sources respectively with the current and voltage values specified by the generic_expression.

The q and phi elements are defined as:

(-1)

(-2)

The r, g, c, and l elements are defined as:

(-3)

(-4)

(-5)

(-6)

The elements r, g, c, and l are provided for compatibility reasons. The correct resistance, conductance, capacitance, and inductance are different from the expressions you specify. For example, a non-linear conductance is defined as:

(-7)

where i and v are the conductance branch current and voltage respectively. If we use the conductance element (equation 5-4), and specify the conductance as a function of the branch voltage:

(-8)

then the true conductance is given by:

(-9)

(-10)

(-11)

Related Topics

Behavioral Source (bsource)

Noise Model for bsource

Temperature Effect on bsource

Circuit Components

Noise Model for bsource

Noise sources are implemented for the elements i, v, r, and g.

Noise for Elements i and v

You need to specify the expression for Power Spectrel Density (PSD) using the white_noise and flicker_noise parameters.

(-12)

(-13)

where simple_expr is the power of the flicker noise (or white noise) source at 1Hz and fexp is the exponent of the frequency.

(-14)

The noise source unit is A²/Hz for i and V²/Hz for v. The following is an example of a noise parameter specification for a current source:

(-15)

where k is the Boltzman constant (1.380626e-23) and

T is the temperature.

(-16)

where V(p,n) is the voltage across the i element.

The following is an example of a noise parameter specification for a voltage source:

(-17)

(-18)

Noise for elements g and r

The syntax is:

name (node1 node2) bsource { r | g }=simple_expr kf=value af=value fexp=value isnoisy={ yes | no }

The white_noise and flicker_noise values are calculated from the above expression. When isnoisy=no, noise contributions are turned off. By default the white noise source is on and the flicker noise source is off (default is kf=0).

The noise source for g is a current source in parallel with the g element and the noise power is in units of A²/Hz. If x is the expression for the g element,

(-19)

(-20)

where kf , af , and fexp are the values specified for these parameters

k is the Boltzman constant (1.380626e-23)

T is the temperature and

v(p,n) is the voltage across the g element.

The noise source for r is a current source in parallel with the r element and the noise power is in units of V²/Hz. If x is the expression for the r element,

(-21)

(-22)

where kf , af , and fexp are the values specified for these parameters

k is the Boltzman constant (1.380626e-23)

T is the temperature and

I(relement) is the current through r element.

Temperature Effect on bsource

The equation for calculating temperature effect is:

(-23)

Related Topics

Behavioral Source (bsource)

Mathematical Definitions

Circuit Components

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