TABLE OF CONTENTS The SPICE Gummel-Poon (SGP) model was for a very long time de facto the standard bipolar model. It was introduced by Gummel and Poon [4, 5], and is described in various textbooks [6, 7]. It is available in virtually every circuit simulator, and modern models can be understood as either extensions or refinements of it. It includes the following effects and features:
Early effect;
Webster effect;
Excess transit time due to base pushout;
Partition of the base-collector capacitance into intrinsic and extrinsic part;
Temperature scaling (impact of ambient temperature on electrical performance).
Since it does not account for dynamic self-heating and collector-charge dependence on current, its capability to describe HBTs is rather limited.
The equivalent circuit of the Gummel-Poon model is shown in Figure 6.1 and its parameters are listed in Table 6.1.
| Parameter | Meaning | Units |
|---|---|---|
| Ideal DC Parameters | ||
| Is | transport saturation current | A |
| Bf | ideal forward current gain | |
| Nf | forward emission coefficient | |
| Br | ideal reverse current gain | |
| Mr | reverse emission coefficient | |
| Parameters of Base Charge q b | ||
| Vaf | forward Early voltage | V |
| Var | reverse Early voltage | V |
| Ikf | forward base high-current injection | A |
| Ikr | reverse base high-current injection | A |
| Nonideal Base Currents | ||
| Ise | BE leakage saturation current | A |
| Ne | BE leakage emission coefficient | |
| Isc | BC leakage saturation current | A |
| Nc | BC leakage emission coefficient | |
| Depletion Capacitances | ||
| Cje | BE zero-bias capacitance | F |
| Vje | BE diffusion voltage |
