Characterizing a semiconductor device, material, or process thoroughly requires the ability to make three types of measurements: precision DC I-V measurements, AC impedance measurements, and ultra-fast I-V measurements. Early high-speed I-V test systems were developed for applications like characterizing high-K dielectrics and SOI isothermal testing. When tested using traditional DC I-V techniques, their insulating substrates cause SOI devices to retain heat, skewing their measured characteristics; testing with pulsed signals reduces this effect.