Memristor Hard-Switching 2

Separate bipolar write pulses and low-voltage read intervals expose two retained resistance states.

Circuit operation

V1 supplies +3 V and −3 V write pulses separated by 0.2 V read intervals. MR1 programs rapidly at 20 MΩ/(V·s). The complete pattern repeats every 6 ms.

Expected behavior

$$I_{read,H}\approx\frac{0.2}{100+10000}$$ $$I_{read,L}\approx\frac{0.2}{100+1000}$$

The positive pulse writes approximately 10 kΩ, giving about 19.8 µA read current. The negative pulse writes approximately 1 kΩ, giving about 181.8 µA. The read level is below threshold, so the current stays at its new value until another write pulse arrives.

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 transient spans 12 ms with a maximum step of 2 µs. The chart uses separate voltage and current lanes, and the table retains the same probe order.

Try a change

Reduce MR1 programming rate Beta to 2 MΩ/(V·s). The same write pulses now move the state only partway toward its limits. Restore the saved values after comparison.

Model limits

MR1 uses the ngspice voltage-threshold memristor model. Alpha is zero, so subthreshold reads preserve state. Rmin, Rmax, Rinit, Vt, and Beta are illustrative values. This is a memristive-system model, not a material-specific or thermal model.

Reference: ngspice memristor model and threshold-model paper.