Junction diodes
Junction Diodes
General form
DXXXXXXX N+ N- MNAME <AREA> <OFF> <IC=VD> <TEMP=T> <AREA=A> <PJ=P>
Examples
DBRIDGE 2 10 DIODE1 DCLMP 3 7 DMOD 3.0 IC=0.2 DJ 5 0 NDIO AREA=2e-12 PJ=6e-6
N+ and N- are the positive and negative nodes, respectively. MNAME is the model name, AREA is the area factor, and OFF indicates an (optional) starting condition on the device for dc analysis. If the area factor is omitted, the model's AREA is used, or 1.0 if it has none. The (optional) initial condition specification using IC=VD is intended for use with the UIC option on the .TRAN control line, when a transient analysis is desired starting from other than the quiescent operating point. The (optional) TEMP value is the temperature at which this device is to operate, and overrides the temperature specification on the .OPTION control line.
PJ is the perimeter of the junction, for the sidewall parameters JSW and CJSW of HSPICE-style models (see the model below); without it, the model's PJ is used, or 0. For a model of LEVEL=3, as HSPICE, AREA and PJ are an area and a length, and are scaled by the .OPTIONS SCALE and GEOSHRINK (AREA by their product squared).
Parameters: Junction diode
Diode Model (D)
The dc characteristics of the diode are determined by the parameters IS and N. An ohmic resistance, RS, is included. Charge storage effects are modeled by a transit time, TT, and a nonlinear depletion layer capacitance which is determined by the parameters CJO, VJ, and M. The temperature dependence of the saturation current is defined by the parameters EG, the energy and XTI, the saturation current temperature exponent. The nominal temperature at which these parameters were measured is TNOM, which defaults to the circuit-wide value specified on the .OPTIONS control line. Reverse breakdown is modeled by an exponential increase in the reverse diode current and is determined by the parameters BV and IBV (both of which are positive numbers).
| name | parameter | units | default | example | area |
|---|---|---|---|---|---|
| IS | saturation current | A | 1.0e-14 | 1.0e-14 | * |
| RS | ohmic resistance | Ω | 0 | 10 | * |
| N | emission coefficient | - | 1 | 1.0 | |
| TT | transit-time | sec | 0 | 0.1ns | |
| CJO | zero-bias junction capacitance | F | 0 | 2pF | * |
| VJ | junction potential | V | 1 | 0.6 | |
| M | grading coefficient | - | 0.5 | 0.5 | |
| EG | activation energy | eV | 1.11 | 1.11 Si 0.69 Sbd 0.67 Ge | |
| XTI | saturation-current temp. exp | - | 3.0 | 3.0 jn 2.0 Sbd | |
| KF | flicker noise coefficient | - | 0 | ||
| AF | flicker noise exponent | - | 1 | ||
| FC | coefficient for forward-bias depletion capacitance formula | - | 0.5 | ||
| BV | reverse breakdown voltage | V | infinite | 40.0 | |
| IBV | current at breakdown voltage | A | 1.0e-3 | ||
| TNOM | parameter measurement temperature | C | 27 | 50 |
HSPICE parameters
Diode models from HSPICE model libraries, such as the junction diodes of foundry libraries (LEVEL=3), can be used. These parameters are understood as well:
| name | parameter | units | default | scaled by |
|---|---|---|---|---|
| CJ, PB, MJ, TREF | the same as CJO, VJ, M and TNOM | |||
| JSW | sidewall saturation current | A/m | 0 | PJ |
| CJSW | sidewall zero-bias junction capacitance | F/m | 0 | PJ |
| PHP (or VJSW) | sidewall junction potential | V | 1 | |
| MJSW | sidewall grading coefficient | - | 0.33 | |
| FCS | sidewall forward-bias depletion capacitance coefficient | - | FC | |
| AREA, PJ | the instances' area and perimeter if they don't give them | 1, 0 | ||
| TLEVC | capacitance temperature equations: 0, as for CJO and VJ above, or 1 (below) | - | 0 | |
| CTA, CTP | temperature coefficients of CJ and CJSW, for TLEVC=1 | 1/°C | 0 | |
| TPB, TPHP | temperature coefficients of PB and PHP, for TLEVC=1 | V/°C | 0 | |
| TCV | temperature coefficient of BV | V/°C | 0 |
The saturation current is IS·AREA + JSW·PJ, and the depletion charge and capacitance are those of the bottom junction (CJO·AREA, VJ, M, FC) and the sidewall junction (CJSW·PJ, PHP, MJSW, FCS) added together. With TLEVC=1, as in HSPICE, CJ, CJSW, PB and PHP change linearly with the temperature T:
CJ(T) = CJ · (1 + CTA·(T - TNOM)) PB(T) = PB - TPB·(T - TNOM) CJSW(T) = CJSW · (1 + CTP·(T - TNOM)) PHP(T) = PHP - TPHP·(T - TNOM)
and with TLEVC=0 the sidewall junction's potential and capacitance change with temperature in the same way as the bottom junction's. TCV lowers the breakdown voltage by TCV per degree. Other TLEVC values are taken as 1. LEVEL, TLEV, IK (or IKF) and IKR are accepted but have no effect: the saturation current's temperature dependence is always the one above, and there is no high-injection knee.
For LEVEL=3 an instance's AREA and PJ are scaled by the .OPTIONS SCALE and GEOSHRINK; see junction diodes.
Parameters: Junction diode