Cascode circuit with high output impedances for the operation with a low supply voltage

摘要

PURPOSE: To provide a cascode circuit capable of lowering the lower limit value of an operating voltage in a CMOS process and enlarging output signal amplitude by responding to input signals supplied from an input terminal and raising the margin of the output signal amplitude obtained from an output terminal by a negative feedback means. ;CONSTITUTION: This circuit is provided with the serial connection circuit of transistors 1 and 2 serially connected between the output terminal 71 and a lower side power-supply potential, the input terminal 70 connected to the gate electrode of the transistor 1, the transistor 3 gate-grounded by a direct connection point and a current mirror circuit composed of the transistor 4 and 5 in the relation of reverse polarity with the transistors 1, 2 and 3 to which a current is supplied from a higher side power supply VDD. Then, the cascode circuit is provided with the negative feedback loop of a gain first stage. Thus, the drain current of the transistor determined by the voltage supplied to the voltage input terminal 70 is hardly influenced by the DC potential of the current output terminal 71. Thus, the output impedance of the cascode circuit is raised.;COPYRIGHT: (C)1995,JPO