Patent ID: 7737783
Filing Date: 2010-06-15
Classification: H03F

Abstract:
1. A differential amplifier comprising: a constant-current source; a first amplification circuit which is connected to the constant-current source, allows a current in accordance with an input signal input from a signal input terminal to flow to a first load, and provides a first output signal that is generated by the first load in accordance with the input signal to a first output terminal; a second amplification circuit which is connected to the constant-current source, allows a current having a magnitude, acquired by subtracting a current value flowing through the first load from a current value flowing through the constant-current value, to a second load, and provides a second output signal generated by the second load to a second output terminal; a transformer which has a primary winding and a secondary winding electromagnetically coupled to the primary winding, a hot side of the primary winding being connected to the signal input terminal, a cold side of the primary winding being connected to the first amplification circuit, the secondary winding having a center tap to which a fixed potential is applied, a hot side of the secondary winding being connected to the second output terminal, and a cold side of the secondary winding being connected to the first output terminal; and a resistor connected between the first output terminal and the signal input terminal.