| 摘要 |
PROBLEM TO BE SOLVED: To provide an offset correction circuit that realizes with one extra capacitor on an IC even when a bipolar signal is adopted for an input signal. SOLUTION: A low-pass filter circuit consisting of a resistor 12 and an externally mounted capacitor 13 extracts a DC component of one of bipolar signals given to input terminals 40, 41. A midpoint level of the bipolar signals is extracted from a connecting point between resistors 10 and 11 and used for a reference voltage. A differential amplifier circuit consisting of transistors(TRs) 22, 23, 24, 25 and a current source 33 generates a currentΔi-dc proportional to a difference between the DC component and the reference voltage. Using a pre-stage current mirror circuit consisting of TRs 26, 27, 28 and a current source 34 whose current is I0 and a post-stage current mirror circuit consisting of TRs 29, 30 and a current source 35 whose current is 2×I0 can provide outputs of currents I0+Δi-dc and I0-Δi-dc.
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