@Muse - The **BSS87** is a 200 V, 260 mA N-channel enhancement-mode DMOS power FET. In EveryCircuit, the level-1 NMOS model uses the standard Shichman-Hodges equations:
$$I_D = \frac{1}{2} K_p \frac{W}{L} (V_{GS} - V_{th})^2 (1 + \lambda V_{DS})$$
### Matching BSS87 Parameters
From the BSS87 datasheet:
- **Threshold voltage ($V_{th}$ / `vto`)**: typically $1.6\text{ V}$ (range $0.8\text{ V}$ to $2.4\text{ V}$).
- **On-resistance ($R_{DS(on)}$)**: $\approx 5.5\ \Omega$ at $V_{GS} = 10\text{ V}$, $I_D = 200\text{ mA}$.
- **Transconductance parameter ($K_p \cdot \frac{W}{L}$)**: with default dimensions $W = 1\,\mu\text{m}$ and $L = 0.2\,\mu\text{m}$ ($\frac{W}{L} = 5$), setting `kp=0.038` ($38\text{ mA/V}^2$) sets effective $K_n = \frac{1}{2} K_p \frac{W}{L} \approx 95\text{ mA/V}^2$, matching typical BSS87 saturation current and transfer characteristics.
- **Channel-length modulation (`lam`)**: set to `0.005` ($0.005\text{ V}^{-1}$) to model the high output resistance expected of a 200 V device.
### Circuit Setup
- #M1 is biased with gate-source voltage #Vgs set to $4\text{ V}$ (well above threshold $V_{th} = 1.6\text{ V}$).
- #Vds delivers a swept drain voltage, with current-limiting resistor #Rd ($10\ \Omega$) protecting against excessive current.
- The oscilloscope is configured in **X-Y mode** plotting drain current through #Rd versus #drain voltage to display the output characteristic curve ($I_D$ vs. $V_{DS}$) showing linear and saturation regions. You can adjust #Vgs to trace curves for different gate voltages.
