OSCILLATIONS IN MULTICHIP POWER MOSFETS.

Power MOSFETs which are connected in parallel on a single header to achieve large current ratings can exhibit differential mode oscillations that are not apparent external to the device package but which generate excessive voltage stress, radiation noise, and power dissipation. This problem is a small-single circuit instability aggravated by the high gain of these devices. Using a small-signal circuit model and the Routh-Hurwitz criterion and SPICE simulations of the circuit's loop gain, the regions of stability for different circuit elements were numerically determined. From this analysis, it was found that multichip MOSFETs can be made free of these oscillations by adjusting the device parameters, particularly the gate resistance, within practical limits.