## 3.17 `Q`: Bipolar Junction Transistor

### 3.17.1 Syntax

`Q` xxxxxxx nc nb ne ns mname {area} {args}
`.BJT` label nc nb ne ns mname {area} {args}

### 3.17.2 Purpose

Bipolar junction transistor,

### 3.17.3 Comments

Nc, nb, ne, and ns are the collector, base, emitter, and substrate nodes, respectively. Mname is the model name.
Area is a unit-less multiplier for the area.
The options `rstray` and `norstray` determines whether or not series resistances are included. `rstray` is the default. `Norstray` is the equivalent of setting the model parameters `rc`, `re`, and `rb` all to zero.
Entering a parameter value of 0 is not the same as not specifying it. This behavior is not compatible with SPICE. In SPICE, a value of 0 is often interpreted as not specified, with the result being to calculate it some other way. If you want it to be calculated, don't specify it.
Another subtle difference from SPICE is that Gnucap may omit some unnecessary parts of the model, which may affect some reported values. It should not affect any voltages or currents. For example, if the gate and drain are tied, Cgs will be omitted from the model, so the printed value for Cgdovl and Cgd will be 0, which will disagree with SPICE. It doesn't matter because a shorted capacitor can store no charge.

### 3.17.4 Element Parameters

#### Basic Spice compatible parameters

`Area` = x
  Junction area. (Default = `1`) This is a scaling parameter, with no relevant actual units.
`OFF`
  (Default = not specified) If this word is specified, the initial guess will assume the device is off.
`TEMP` = x
  Junction temperature. (Default = the global temperature.)
`ICVBE` = x
  Initial condition, Vbe. (Default = NA) Use this as the initial condition, when the `UIC` option is specified. The syntax is different from Spice, but the function is the same.
`ICVCE` = x
  Initial condition, Vce. (Default = NA) Use this as the initial condition, when the `UIC` option is specified. The syntax is different from Spice, but the function is the same.

### 3.17.5 Model Parameters

#### Basic DC parameters

`BF` = x
  Ideal maximum forward beta. (Default = 100) Alternate name is `BFM`.
`BR` = x
  Ideal maximum reverse beta. (Default = 1) Alternate name is `BRM`.
`IBC` = x
  BC Transport saturation Current per area. (Default = IS) If omitted, `IS` is used. You should specify either `IS` or `IBC`, not both.
`IBE` = x
  BE Transport saturation Current per area. (Default = IS) If omitted, `IS` is used. You should specify either `IS` or `IBE`, not both.
`IS` = x
  Transport saturation Current per area. (Default = 1e-16) If `IBE` and `IBC` are specified, they are used instead. Do not specify both.
`NF` = x
  Forward current emission coefficient. (Default = 1)
`NR` = x
  Reverse current emission coefficient. (Default = 1)

#### Base width modulation

`VAF` = x
  Forward Early voltage. (Default = Infinite) Alternate names are `VA` and `VBF`.
`VAR` = x
  Reverse Early voltage. (Default = Infinite) Alternate name is `VB`.

#### Low current beta degeneration

`ISC` = x
  B-C leakage saturation current. (Default = c4 * is)
`C4` = x
  B-C leakage scale factor. (Default = 0) Alternate name is `JLC`.
`NC` = x
  B-C leakage emission coefficient. (Default = 2)
`ISE` = x
  B-E leakage saturation current. (Default = c2 * is)
`C2` = x
  B-E leakage scale factor. (Default = 0) Alternate name is `JLE`.
`NE` = x
  B-E leakage emission coefficient. (Default = 1.5)

#### High current beta degeneration

`IKF` = x
  Forward beta roll-off corner current. (Default = Infinite) Alternate names are `JBF` and `IK`.
`IKR` = x
  Reverse beta roll-off corner current. (Default = Infinite) Alternate name is `JBR`.

#### Parasitic resistance

`IRB` = x
  Current for base resistance=(rb+rbm)/2". (Default = Infinite) Current where base resistance falls halfway to its minimum value. Alternate name is `JRB`.
`RB` = x
  Zero bias base resistance. (Default = 0)
`RBM` = x
  Minimum base resistance at high current. (Default = rb)
`RE` = x
  Emitter resistance. (Default = 0)
`RC` = x
  Collector resistance. (Default = 0)

#### Junction capacitance

`CJC` = x
  Zero bias B-C depletion capacitance. (Default = 0)
`CJE` = x
  Zero bias B-E depletion capacitance. (Default = 0)
`CJS` = x
  Zero bias C-S capacitance. (Default = 0) Alternate name is `CCS`.
`FC` = x
  Coefficient for forward-bias depletion capacitance formula. (Default = .5)
`MJC` = x
  B-C junction grading coefficient. (Default = .33) Alternate names are `MJ` and `MC`.
`MJE` = x
  B-E junction grading coefficient. (Default = .33) Alternate name is `ME`.
`MJS` = x
  Substrate junction grading coefficient. (Default = 0) Alternate names are `MS` and `MSUB`.
`VJC` = x
  B-C built in potential. (Default = .75) Alternate name is `PC`.
`VJE` = x
  B-E built in potential. (Default = .75) Alternate name is `PE`.
`VJS` = x
  Substrate junction built in potential. (Default = .75) Alternate name is `PS`.
`XCJC` = x
  Fraction of B-C capacitance connected to internal base node. (Default = 1)

#### Parasitic capacitance

`CBCP` = x
  External B-C constant parasitic capacitance. (Default = 0)
`CBEP` = x
  External B-E constant parasitic capacitance. (Default = 0)
`CBSP` = x
  External B-S constant parasitic capacitance for lateral transistors. (Default = 0)
`CCSP` = x
  External B-C constant parasitic capacitance for vertical transistors. (Default = 0)

#### Transit time

`ITF` = x
  High current dependence of TF. (Default = 0)
`PTF` = x
  Excess phase at freq=1.0/(TF*2PI) Hz. (Default = 0)
`TF` = x
  Ideal forward transit time. (Default = 0)
`TR` = x
  Ideal reverse transit time. (Default = 0)
`VTF` = x
  Voltage giving VBC dependence of TF. (Default = Infinite)
`XTF` = x
  Coefficient for bias dependence of TF. (Default = 0)

#### Temperature effects

`XTB` = x
  Forward and reverse beta temperature exponent. (Default = 0)
`XTI` = x
  Temperature exponent for effect on IS. (Default = 3)
`EG` = x
  Energy gap for IS temperature dependency. (Default = 1.11)
`TNOM` = x
  Parameter measurement temperature, Celsius. (Default = 27)

### 3.17.6 Probes

`VBEInt`
  Base-emitter internal voltage.
`VBCInt`
  Base-collector internal voltage.
`VBXInt`
  External base to internal base voltage.
`VCSInt`
  Collector-substrate internal voltage.
`VBS`
  Base-substrate voltage.
`VBE`
  Base-emitter voltage.
`VBC`
  Base-collector voltage.
`VCS`
  Collector-substrate voltage.
`VCB`
  Collector-base voltage.
`VCE`
  Collector-emitter voltage.
`VES`
  Emitter-substrate voltage.
`VEB`
  Emitter-base voltage.
`VEC`
  Emitter-collector voltage.
`VB`
  Base-ground voltage.
`VC`
  Collector-ground voltage.
`VE`
  Emitter-ground voltage.
`VS`
  Substrate-ground voltage.
`VBI`
  Internal Base-ground voltage.
`VCI`
  Internal Collector-ground voltage.
`VEI`
  Internal Emitter-ground voltage.
`ICE`
  Collector-emitter current.
`ICEOffset`
  Offset part of ICE.
`GO`
  Output (collector-emitter) conductance.
`GM`
  Transconductance.
`IPI`
  Base-emitter current.
`IPIOffset`
  Offset part of IPI.
`GPI`
  Base-emitter conductance.
`IMU`
  Base-collector current.
`IMUOffset`
  Offset part of IMU.
`GMU`
  Base-collector conductance.
`IB`
  Base current.
`GX`
  Conductance of base spreading resistance.
`RX`
  Base spreading resistance.
`IC`
  Collector current.
`IE`
  Emitter current.
`QBX`
  External Base-collector charge.
`CQBX`
  External Base-collector capacitance.
`CBX`
  External Base-collector capacitance (CQBX).
`QBC`
  Internal Base-collector charge.
`CQBC`
  Internal Base-collector capacitance.
`CBC`
  Internal Base-collector capacitance (CQBC).
`CMU`
  Internal Base-collector capacitance (CQBC).
`QCS`
  Collector-substrate charge.
`CQCS`
  Collector-substrate capacitance.
`CCS`
  Collector-substrate capacitance (CQCS).
`QBE`
  Base-emitter charge.
`CQBE`
  Base-emitter capacitance.
`CBE`
  Base-emitter capacitance. (CQBE).
`CPI`
  Base-emitter capacitance. (CQBE).
`P`
  Power.
`PD`
  Power dissipated. The power dissipated as heat. It is always positive and does not include power sourced. It should be the same as P because transistors cannot generate energy.
`PS`
  Power sourced. The power sourced by the part. It is always positive and does not consider its own dissipation. It should be 0 because transistors cannot generate energy.

All parameters of the internal elements (Ice, Ipi, Imu, Rc, Re, Yb, Cbx, Cbc, Ccs, Cbe, Cbcp, Cbep, Cbsp, Ccsp) are available. To access them, concatenate the labels for the internal element with this device, separated by a dot. Cbe.Q6 is the base to emitter capacitance of Q6.
In this release, there are no probes available in AC analysis except for the internal elements.