US Patent 7461285 Programmable resistor array having current leakage control

A free running clock circuit includes a programmable resistor array including a plurality of resistors connected in series. A plurality of transistors are connected to the plurality of resistors wherein each of the plurality of resistors has one of the plurality of transistors associated therewith for connecting a resistor to the first programmable resistor and providing a resistance thereto. A transistor funnel limits leakage currents from a portion of the plurality of transistors to a single transistor of the transistor funnel.