COMPARATOR CIRCUIT

PURPOSE:To utilize a switching characteristic of a transistor(TR) sufficiently and to improve the gain by constituting a circuit comparing a signal voltage with a reference voltage with a single end circuit and a source follower circuit, and connecting the source of an input side transmission of the single end circuit to the source follower circuit. CONSTITUTION:The drain of an input side TR Q11 connects to a power voltage VDD via an active load TR Q12b whose gate and source are short-circuited and forms a single end circuit A using the drain of the TR Q11 as an output terminal. A source of the TR Q11 connects to a source follower circuit B. If a signal fed to the input side TR Q11 of the single end circuit A is fluctuated, since the output impedance is small, the source of the input side TR Q11 has no voltage fluctuation and a voltage equal to the reference voltage always appears at the source level. Thus, even when the signal voltage gets higher than the reference voltage, the switching characteristic of the input side TR Q11 is sufficiently displayed and a large gain is obtained.