Patent ID: 7619620

Claim:
A test circuit for detecting an output signal from a driving circuit, comprising: a judging circuit which outputs a detection signal when the output signal output from the driving circuit has one polarity, but does not output the detection signal when the output signal has the other polarity; and an amplifying circuit which amplifies the signal from the judging circuit, wherein the driving circuit is a demultiplexer which, if a control signal and an inverted control signal obtained by inverting the control signal are input, has a plurality of transfer gates to be turned on/off in synchronization with the control signal and the inverted control signal, and the judging circuit has a plurality of NOT circuits which individually invert the inverted control signal, a plurality of NAND circuits which correspondingly invert logical products of the output signals from the individual NOT circuits and the control signal corresponding to the inverted control signal, and output the inverted logical products, and a NOR circuit which calculates a negative logical product of the output signals from the plurality of NAND circuits.