| 摘要 |
PURPOSE:To make a high-precision integrating circuit needless by snychronizing chopper pulse CHP and switching pulse SWP with each other and by operating an A/D conversion synchronously with CHP. CONSTITUTION:Analogue signal AI input to chopper circuit 1 is chopped according to CHP82 synchronized with SWPs 43 and 44, and the output signal is input to synchronous rectifying circuit 2. In circuit 2, the input signal is subjected to synchronous rectification according to synchronizing pulse 83 from control circuit 8, and output signal 22 is input to sample hold SH circuit 5. In circuit 5, the voltage value of signal 22 is held at the rise of SH signal 85 synchronized with the rise or the fall of SWPs 43 and 44 according to A/D conversion command signal 84 input arbitrarily to circuit 8, and output signal 51 is given to A/D converter 6. A/D conversion is started by A/D conversion start signal 86 synchronized with the fall of signal 85, and thus performing A/D conversion during absence of the influence of noise dependent upon CHP and SWPs. Since A/D conversion is performed synchronously with CHP, it is unnecessary to integrate the synchronous rectification signal. |
