US Patent 7782128 Sign detection device and associated method

A sign detection device including a first comparing device for comparing a first input signal with a first threshold signal in a first period and a second period to generate a first output signal; a second comparing device for comparing a second input signal with a second threshold signal to generate a second output signal; a converter for optionally changing the polarity of the second output signal to obtain a third output signal; and an operator coupled to the first comparing device and the converter for performing a logic operation of the first output signal and the third output signal to obtain polarity information of the product of the first input signal and the second input signal.