A current amplifier and a transmitter using the same. The current amplifier includes: a first transistor having a gate coupled to a former-stage circuit, a drain coupled to a current source, and a source biased at a constant voltage level; a second transistor having a gate coupled to the current source and having a source and a drain; a first impedance circuit coupled between the gate of the first transistor and the source of the second transistor; and a second impedance circuit coupled between the source of the second transistor and a ground terminal. The current amplifier receives an input current from the former-stage circuit and generates an output current at the drain of the second transistor. Note that no current source is connected to the source of the first transistor.