Patent ID: 7911279
Filing Date: 2011-03-22
Classification: H03F

Abstract:
1. An amplifying device, comprising: a cascode amplifier configured to receive an input signal and to output an amplified output signal corresponding to the input signal, the cascode amplifier comprising first and second cascode transistors, wherein the first cascode transistor is connected to an input node for receiving the input signal, and the second cascode transistor is connected to a voltage source and an output node for outputting the amplified output signal; and a biasing circuit configured to bias the cascode amplifier, the biasing circuit comprising a first current mirror and a second current mirror stacked on the first current mirror, the first current mirror comprising the first cascode transistor of the cascode amplifier, and the second current mirror directly biasing the second cascode transistor of the cascode amplifier, wherein the biasing circuit improves linearity of the cascode amplifier, and minimizes changes to a drain voltage and a drain current of the first cascode transistor, wherein the first current mirror further comprises a first mirror transistor having a gate connected to a gate of the first cascode transistor, and wherein the second current mirror comprises a second mirror transistor having a same current as the first mirror transistor and a third mirror transistor having a gate connected to a gate of the second mirror transistor, the current of the second mirror transistor being mirrored into the third mirror transistor as a bias current of the cascode amplifier.