Patent ID: 7944303

Claim:
A source follower circuit comprising: a first MOSFET having a gate coupled to an input signal, a source coupled to a first output, and a drain; a high impedance circuit providing current coupled to the first MOSFET drain; a difference amplifier having two inputs, one input coupled to the first MOSFET drain, and the other input, coupled to a reference voltage, said amplifier having an output connected to the gate of a second MOSFET that has a drain coupled to the said first output, wherein gm 1 is the transconductance of the first MOSFET, gm 2 is the transconductance of the second MOSFET, Av is the gain of the difference amplifier, and wherein the source follower circuit output impedance is Rout=1/(gm 1 *gm 2 *ro 1 *Av), where ro 1 is the output impedance of the first MOSFET, wherein the source follower circuit maintains the drain of the first MOSFET equal to the reference voltage.