5.5.2 Pulse Shape and Amplitude

The derivative of the static hysteresis curve has a distinct maximum near the coercive field and a minimum at saturation. Accordingly, the transient effects caused by the related transient term (5.4) show similar properties.

Consequently the response will depend on the pulse shape. The different hysteresis curves obtained for sinusoidal and triangular pulses are plotted in Fig. 5.6 and Fig. 5.7. A comparison between these two plots shows two systematic differences

• The coercive field increases much faster when sinusoidal pulses are applied.
• The hysteresis loop shows a higher tendency to close when triangular pulses are applied.

The first of these two effects is caused by the higher derivative of the sinusoidal input signal at 0V, which increases the related transient term (5.3).

The second effect is related to the fact that sinusoidal pulses remain near their amplitude for a comparatively longer period. This leads to an increased relaxation, as the derivative of the static hysteresis curve has a distinct minimum near saturation, which minimizes transient effects caused by the related transient term (5.4).

Figure 5.6: Signal response as function of frequency, sinusoidal pulse

Figure 5.7: Signal response as function of frequency, triangular pulse

This behavior can clearly be seen in Fig. 5.8, which shows the results obtained for a series of sinusoidal pulses with different amplitudes at a fixed frequency of 1MHz. As expected, field reversal occurs near the turning point, where the term (5.4) has its minimum, independently of the amplitude.

Figure 5.8: Signal response as function of amplitude, sinusoidal input with 1MHz

Figure 5.9: Charge and current response of a voltage step

Figure 5.10: Charge and current response of a transient simulation