Bake apparatus for use in baking a substrate, such as a semiconductor wafer, includes a chamber, a hot plate installed within the chamber, and first and second buffer plates for uniformly dispersing hot gas. The drug delivery pump can be external or implantable infusion pump coupled with a drug infusion catheter extending to the site. The power supply unit includes a gate driving circuit that has a power MOSFET transistor which, under the control of a PWM controller, produces a switched DC signal.