The subthreshold slope is a feature of a MOSFET's current–voltage characteristic. In the subthreshold region, the drain current behaviour—though being controlled by the gate terminal—is similar to the exponentially decreasing current of a forward biased diode. Therefore, a plot of drain current versus gate voltage with drain, source, and bulk voltages fixed will exhibit approximately log-linear behaviour in this MOSFET operating regime. Its slope is the subthreshold slope. The subthreshold slope is also the reciprocal value of the subthreshold swing Ss-th which is usually given as: C_d = depletion layer capacitance C_{ox} = gate-oxide capacitance = thermal voltage The minimum subthreshold swing of a conventional device can be found by letting and/or, which yield (known as thermionic limit) and 60 mV/dec at room temperature (300 K). A typical experimental subthreshold swing for a scaled MOSFET at room temperature is ~70 mV/dec, slightly degraded due to short-channel MOSFET parasitics. A dec (decade) corresponds to a 10 times increase of the drain current ID. A device characterized by steep subthreshold slope exhibits a faster transition between off (low current) and on (high current) states.