Patent ID: 7633344
Filing Date: 2009-12-15
Classification: H03F

Abstract:
1. A low noise amplifier comprising: a transformer having a primary winding whose one end is connected to a signal input terminal to which an input signal is applied, and a secondary winding electromagnetically coupled to the primary winding; an input-stage transistor having a control electrode, a first conduction electrode and a second conduction electrode, the first and second conduction electrodes changing a conduction state by the control electrode, and the control electrode being connected to a terminal of the primary winding other than the terminal connected to the signal input terminal; an upper-stage transistor having a control electrode, a first conduction electrode and a second conduction electrode, the first and second conduction electrodes changing a conduction state by the control electrode, the second conduction electrode being connected to a load device, and the first conduction electrode being connected to the second conduction electrode of the input-stage transistor so that the upper-stage transistor is connected to the input-stage transistor in a cascode connection manner, thereby enhancing an output impedance; an amplification-result transmission circuit providing an amplification result of the input signal to an output node; a first negative feedback circuit applying an amplification result of the input signal on the output node to the secondary winding; a second negative feedback circuit connected between the output node and the signal input terminal; a first phase compensation circuit connected to the output node and the control electrode of the upper-stage transistor; and a second phase compensation circuit connected to the output node and the control electrode of the input-stage transistor.