The Shockley diode equation or the diode law, named after transistor co-inventor William Shockley of Bell Telephone Laboratories, gives the I–V (current-voltage) characteristic of an idealized diode in either forward or reverse bias (applied voltage): where I is the diode current,IS is the reverse bias saturation current (or scale current),VD is the voltage across the diode,VT is the thermal voltage kT/q (Boltzmann constant times temperature divided by electron charge), andn is the ideality factor, also known as the quality factor or sometimes emission coefficient.