The invention concerns a circuit comprising: a first transistor (102) having first and second main current nodes, and a gate node adapted to receive a first timing signal (CLK) for causing the first transistor to transition between conducting and non-conducting states; a biasing circuit (108) coupled to a further node of said first transistor; and a control circuit (110) adapted to control said biasing circuit to apply a first control voltage (VCTRL) to said further node to adjust the timing of at least one of said transitions.