Tunnel Diode I/V Curve

Sweep through the peak, negative differential resistance region, valley, and ordinary forward-conduction branch.

Circuit operation

V1 is swept from −0.1 V to +0.7 V in 1 mV increments. The current probe reports positive anode-to-cathode current. The generic model has a 5 mA peak at 0.1 V and a 0.5 mA valley at 0.4 V.

Expected behavior

$$r_d=\frac{dV}{dI}$$ $$\begin{gathered}r_d=\frac{V_v-V_p}{I_v-I_p}\\r_d\approx-66.7\,\Omega\end{gathered}$$

Between the peak and valley, increasing forward voltage reduces current. The diode still consumes positive DC power there: negative differential resistance concerns the slope, not a negative value of V/I. Reverse conduction and the rising branch above the valley are also visible.

Reading the results

The first voltage probe is green; the second, when present, is red. The first current probe is blue. The schematic opens fitted to its extents. The saved DC sweep uses voltage on the horizontal axis. Voltage and current occupy separate chart lanes; the table preserves both measured quantities.

Try a change

Set D1 peak current to 3 mA. The peak-to-valley ratio and magnitude of the negative differential slope decrease. Restore the saved values after comparison.

Model limits

The diode uses a continuous piecewise-linear I/V curve with constant junction capacitance. It captures peak/valley behavior and negative differential resistance, but does not predict a particular diode’s tunneling physics, temperature behavior, noise, or high-frequency parasitics.

Reference: tunnel-diode modeling.