A DC level wandering cancellation circuit is provided. The DC level
wandering cancellation circuit comprises a low pass filter, for receiving
an input voltage; a high pass filter coupled to the low pass filter; an
amplifier coupled to the high pass filter for receiving a reference
voltage and an output signal of the high pass filter; a comparator
coupled to the amplifier for receiving an output signal of the amplifier
to compare the reference voltage with the output signal of the amplifier;
a resistor coupled between outputs of the high pass filter and the
amplifier; a control logic coupled to the comparator for receiving a
compared result from the comparator; and a switching means coupled
between the high pass filter and the output of the amplifier. The
switching means is turned on for a predetermined interval by the control
logic according to the compared result.