IGT-gated bipolar MOS hybrid cascode switch

A three-terminal combinational switch which employs an insulated gate transistor (IGT) as a driver for a bipolar transistor in cascode with a low-voltage MOSFET is proposed. The desirable and limiting characteristics of IGT and IGT/bipolar cascode connection are reviewed. The operation details, advantages and device selection criteria of the proposed switch are discussed. The hybrid switch has improved performance over IGT/bipolar cascode and FET-gated bipolar transistor (FGT) switches. Compared to FGT, the proposed switch has decreased on-state drop, decreased chip area requirement, and higher dv/dt rating. This allows its use in high-voltage, high-current and high-frequency switching converters. Experimental results obtained using this switch (implemented using the discrete devices) in a chopper circuit are presented.<
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