A programmable capacitance circuit including an input node; an output
node; and a plurality of capacitance stages. Each of the capacitance
stages is coupled to the input node and the output node, and wherein each
capacitance stage is configured to be switched into a circuit path
between the input node and the output node. Each of the capacitance
stages includes a capacitor, and a control transistor having a gate
capacitance in series with the capacitor, wherein the gate capacitance is
configured to be added to the capacitance of the capacitor between the
input node and the output node.