A noise removal circuit for removing spike-shaped noise from an electrical signal, comprising: a signal amplifying section that is configured to receive the electrical signal and amplify the electrical signal; and an amplification control section that is configured to control the amplification factor of the signal amplifying section for the electrical signal according to the voltage of the electrical signal, wherein the amplification control section puts a limit on the amplification factor of the signal amplifying section such that the amplification factor decreases as the voltage of the electrical signal increases; wherein the signal amplifying section has a differential amplifier circuit configured to amplify the electrical signal and output the amplified signal; characterised in that the amplification control section has a signal converting section configured to convert a control signal formed based on the electrical signal into a current signal, and a current mirror circuit configured to change a control current of the differential amplifier circuit based on the current signal received from the signal converting section to thereby control the amplification factor of the signal amplifying section, wherein the amplification control section uses the current mirror circuit to control the control current, limiting the amplification factor of the signal amplifying section, in order to prevent the output of the differential amplifier circuit from exceeding a predetermined value; and further characterised in that the noise removal circuit comprises: a control voltage generating circuit configured to extract a center value of a ripple component from the electrical signal as a change component of the electrical signal and output the change component as an output signal; and a signal inverting circuit configured to vertically invert the waveform of the output signal from the control voltage generating circuit and output the resulting signal, wherein the control signal is output from the signal inverting circuit and input to the signal converting section. a signal amplifying section that is configured to receive the electrical signal and amplify the electrical signal; and an amplification control section that is configured to control the amplification factor of the signal amplifying section for the electrical signal according to the voltage of the electrical signal, wherein the amplification control section puts a limit on the amplification factor of the signal amplifying section such that the amplification factor decreases as the voltage of the electrical signal increases; wherein the signal amplifying section has a differential amplifier circuit configured to amplify the electrical signal and output the amplified signal; characterised in that the amplification control section has a signal converting section configured to convert a control signal formed based on the electrical signal into a current signal, and a current mirror circuit configured to change a control current of the differential amplifier circuit based on the current signal received from the signal converting section to thereby control the amplification factor of the signal amplifying section, wherein the amplification control section uses the current mirror circuit to control the control current, limiting the amplification factor of the signal amplifying section, in order to prevent the output of the differential amplifier circuit from exceeding a predetermined value; and further characterised in that the noise removal circuit comprises: a control voltage generating circuit configured to extract a center value of a ripple component from the electrical signal as a change component of the electrical signal and output the change component as an output signal; and a signal inverting circuit configured to vertically invert the waveform of the output signal from the control voltage generating circuit and output the resulting signal, wherein the control signal is output from the signal inverting circuit and input to the signal converting section. a control voltage generating circuit configured to extract a center value of a ripple component from the electrical signal as a change component of the electrical signal and output the change component as an output signal; and a signal inverting circuit configured to vertically invert the waveform of the output signal from the control voltage generating circuit and output the resulting signal, wherein the control signal is output from the signal inverting circuit and input to the signal converting section.