| 摘要 |
PURPOSE:To attain stable and high speed signal readout by using a current mirror circuit subject to constant current bias for an input section so as to compensate the defect of a contact type image sensor having a large sensor output capacitance. CONSTITUTION:A Wilkinson type current mirror circuit is constituted by each three elements of transistors (TRs) Q1, Q2, a diode D1, or TRs Q6, Q7, a diode D4 or TRs Q10, Q11 and a diode D6, and the diodes D2, D3 or TRs Q22, Q23 are used for biasing. The operating current in a transconductance amplifier as above is set by a current flowing to an amplifier bias terminal 7. When the differential input stage is balanced, no current flows out of a push-pull output 6. A diode bias terminal 3 is connected to ground to apply constant current bias to a non-inverting input 2 and an inverting input 4. The bias current ratio at terminals 3, 7 is a current amplification factor of the amplifier. A signal charge led out of the image sensor output terminal connected to the input 2 is outputted from an output 6 while being multiplied by the current amplification factor.
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