| 摘要 |
PROBLEM TO BE SOLVED: To provide the gain range changeover circuit for an amplifier circuit where a response speed up to range changeover is enhanced by selecting a time constant of an integration circuit in response to a level of an input signal. SOLUTION: An integration circuit 13 has two time constants (t). In the case that a switch SW is closed and the 'small' time constant (t) is selected, the circuit 13 provides an integration operation with a fast response. In the case that the switch SW is open and the 'large' time constant (t) is selected, the circuit 13 provides an integration operation with a comparatively slow response. The integration circuit 13 integrates photo detection signals received from an amplifier 2 with each time constant (t) and provides an output of its integration signal to a CPU 18 and comparators 11, 12 via a buffer 14.
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