MULTI-VALUE IDENTIFICATION CIRCUIT

摘要

PURPOSE:To return the circuit form the pseudo pull-in state to the normal pull-in state quickly by adding a discriminating circuit detecting the pseudo pull-in state and a switching circuit switching an offset control signal. CONSTITUTION:A decision circuit 29 supervises a part of signal 33 of an output signal 15 of an A/D converter 14 and decides whether it is in the normal pull-in state or the pseudo pull-in state and outputs a deciding signal 31. Furthermore, the switching circuit 28 to which offset control signals 26, 27 from a control circuit 25 are supplied outputs selectively an optimum offset control signal 32 in response to the pull-in state based on the deciding signal 31 from the decision circuit 29. Since a gain and an offset of a DC amplifier 12 is controlled optimizingly even in the pseudo pull-in state, the state is restored quickly from the pseudo pull-in state to the normal pull-in state.