| 摘要 |
<p>One of analog input voltages applied to a plurality of analog input terminals (CH1, CH2) is selected by means of analog switches (P1, N1, P2, N2) connected to the respective analog input terminals (CH1, CH2) and supplied to a common terminal (A). In this case, each of the analog switches (P1, N1, P2, N2) permits selective supply of the potential of a corresponding one of the plurality of analog input terminals (CH1, CH2) in response to a control signal supplied from a controller (12). The common terminal (A) is connected to the positive input terminal of a comparator (1). The comparator (1) compares the voltage with a digital output value from the controller (12) which is converted into an analog voltage by means of a D/A converter (2). Further, the controller (12) generates a preset control signal ( phi PR) in an inhibition period during which supply of a voltage from the plurality of analog input terminals (CH1, CH2) to the common terminal (A) is inhibited. An initial potential setting circuit (11) sets the potential of the common terminal (A) to a voltage level equal to substantially one-half the maximum voltage level of the analog input voltages applied to the plurality of analog input terminals (CH1, CH2).</p> |
