(1) Field of the Invention
The present invention relates to a differential circuit for producing an output in response to the difference between two inputs and, especially, to a differential circuit in which the output error of the circuit, occurring when one of the two inputs falls below the lower limit of the ordinary operation range, can be prevented.
(2) Description of the Prior Art
Generally, a differential circuit, such as a comparator or an operational amplifier, which produces an output in response to the difference of two inputs, is designed so as to operate normally only when the variation of the input signals remains between voltage supply level and the ground level. For example, if the voltage supply V.sub.CC is +5 V, a comparison is made of the two inputs in the range between 0 V and +5 V, i.e., the positive voltage range. Conventional comparator circuits, however, cannot operate normally when an input becomes negative due to noise etc.