of electrical parameters due to the process spread and of the operating temperature therefore in first approximation msn and msp are both biased with a same ivgs in fact msn is biased by the control voltage vc while msp is biased by the difference vdd vc both referred to ground potential the allowed range of variation for the control voltage vc may be set as by assuming the node a charged to vdd the node b is also charged to vdd and therefore the transistor m1p is on while the transistor m1n is off in these conditions mtn is off and mtp is on when the reaction node of the ring oscillator switches m1n conducts and msn starts to discharge the node a by a constant current the voltage on the node b tracks the voltage of the node a where the v tp is the threshold voltage of the transistor mtp the transistor mtp turns off too thus the node b is practically disconnected from the node a and clamped to the voltage v1 the transistor msn continues to discharge the node a through a linear voltage ramp where v tn is the threshold voltage of the transistor mtn mtn rams on the charge distributes itself over the nodes a and b the voltage v b is pulled down toward the voltage v a.