Patent 7518435 was granted and assigned to Broadcom (company) on April, 2009 by the United States Patent and Trademark Office.
A power-down biasing circuit includes a current source connected to a drain of a first NMOS transistor through a first switch. A gate of the first NMOS transistor is connected to the current source, and a source of the first NMOS transistor is connected to ground. A first pre-chargeable capacitor is connected between the gate of the first NMOS transistor and ground. A plurality of NMOS transistors form a current multiplier and have gates connected to the current reference. A plurality of current mirrors are connected to drains of the plurality of NMOS transistors and to output switches. Each current mirror has a first PMOS transistor whose drain is connected to a drain of a corresponding one of the plurality of NMOS transistors through a second switch, whose gate is connected to the drain of the corresponding one of the plurality of NMOS transistors and whose source is connected to a supply voltage; a second capacitor is connected between the gate of the first PMOS transistor and the supply voltage; and at least two PMOS transistors are connected as a current multiplier to the output switches. Cascode equivalent biasing circuits are described also.