VOLTAGE FOLLOWER CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a voltage follower circuit, using a fully differential amplifier, that allows starting up regardless of voltage levels of differential input and output terminals at an initial state.SOLUTION: A differential pair circuit 11 constituting a voltage follower circuit 1 has a two-stage amplifier configuration. NMOS transistors TN3 and TN4 provided with the second amplifier are connected to differential output terminals OUTN and OUTP, are driven by PMOS transistors TP1 and TP2 and NMOS transistors TN1 and TN2, and output differential output signals. Current sources IS1 and IS2 aids the drive of the NMOS transistors TN3 and TN4. PMOS transistors TP6 and TP7 limit currents in which the NMOS transistors TN1 and TN2 pass at the time of start-up. When voltage levels of the differential output terminals OUTP and OUTN are a power-supply voltage VDD at an initial state, the operation of the circuit can be started by lowering the voltage levels.