A differential amplifier circuit section (10), which realizes a reduction in power consumption of a signal amplification device, converts an input voltage signal into a current signal and then outputs the signal to a current mirror circuit section (12). Because an input-side current path of the current mirror circuit section (12) does not include a resistor and a current signal is not converted into a current signal at an output terminal (14) of the differential amplifier circuit section (10), a power supply voltage (V.sub.DD) can be reduced to the value of product of source-drain voltages of transistors (MP2, MN2, and MN3). The current signal supplied to the input-side current path of the current mirror circuit section (12) is mirrored in the output-side current path and is then converted into a voltage signal through a resistor (R.sub.L) disposed in the path to be generated from an output terminal (18).