Output characteristics of insulated gate bipolar transistor modules and improvement with substrate control

Improved (constant current) output characteristics of the insulated gate bipolar transistor are theoretically attainable by reducing the minority carrier diffusion length, but the improvements are only observable in practice with low duty cycle or cold (isothermal) curve tracer characteristics. The self-heating of continuously operated transistors increases the output slope conductance in practical applications, and this is shown quantitatively to be in agreement with temperature-dependent theory. The desirable feature of a high output slope resistance of such a MOS-bipolar power device can be adjusted in a controllable manner by application of substrate (body) feedback to a MOSFET driver. This method, which avoids interference with the input impedance of the control gate, has been tested using discrete components in order to demonstrate the feasibility for an integrated power module.