| 摘要 |
PURPOSE:To eliminate erroneous information along with earlier return of a time constant circuit, by short-circuiting a resistance of the time constant circuit with a switch section which operates by an output of a judging section. CONSTITUTION:A detector section 8 is connected to an output of a low-frequency amplifying section 7 which it 8 is connected in parallel to a discriminator section 9 which is formed an opposite phase amplifier, for example, by reversing an input terminal of an operational amplifier. While the detector section 8 is a circuit which generates an output when an output of a detector section 6, namely, the potential at the point Vd falls, the discriminator section 9 produces an output when the potential at the point Vd rises. Therefore, the discriminator section 9 produces an output when an object to be detected leaves a sensor section 2. The output of the discriminator section 9 is applied to an analog switch SW1 of a switch section 10 to short-circuit a resistance Rt determining the time constant of the low-frequency amplifier section 7 connected in parallel to the switch SW 1. This achieves a quick return of the circuit to handle continuous access while eliminating erroneous information otherwise depending on points, remote and close, thereby upgrading practicability. |
