US 10,868,505 B1 · CMOS input stage circuits and related methods

Abstract

Embodiments of improved CMOS input stage circuits and related methods are provided herein to maintain a near constant transconductance across an entire common-mode input voltage range of the input stage. One embodiment includes a pair of NMOS input transistors and a pair of PMOS input transistors, each coupled to receive a differential input voltages at their gate terminals; a current source coupled to source terminals of the pair of PMOS input transistors and configured to generate a current; a current steering circuit configured to steer the current to the pair of NMOS input transistors and/or to the pair of PMOS input transistors, depending on whether a common mode input voltage (CMV) is greater than, less than, or substantially equal to a cross-over voltage; and a current stealing circuit configured to reduce the current when the CMV is substantially equal to the cross-over voltage.

Claims21

Dependent claims

A complementary metal-oxide-semiconductor (CMOS) input stage circuit, comprising:

a pair of NMOS input transistors and a first pair of PMOS input transistors, each coupled to receive differential input voltages at gate terminals thereof;
a first current source coupled to source terminals of the first pair of PMOS input transistors and configured to generate a first current;
a current steering circuit coupled to receive a cross-over voltage and configured to steer the first current to the pair of NMOS input transistors or to the first pair of PMOS input transistors or to both, depending on whether a common-mode input voltage is significantly greater than, significantly less than or substantially equal to the cross-over voltage;
and
a current stealing circuit coupled to receive the cross-over voltage and configured to steal a portion of the first current, so that a smaller remaining portion of the first current is divided among the pair of NMOS input transistors and the first pair of PMOS input transistors when the common-mode input voltage is substantially equal to the cross-over voltage.

2 more elements

A method for a complementary metal-oxide-semiconductor (CMOS) input stage circuit comprising a pair of NMOS input transistors and a first pair of PMOS input transistors, the method comprising:

supplying differential input voltages to gate terminals of the pair of NMOS input transistors and the first pair of PMOS input transistors;
steering a first current to the pair of NMOS input transistors or to the first pair of PMOS input transistors or to both, depending on whether a common-mode input voltage is significantly greater than, significantly less than or substantially equal to a cross-over voltage;
and
stealing a portion of the first current, so that a smaller remaining portion of the first current is divided among the pair of NMOS input transistors and the first pair of PMOS input transistors when the common-mode input voltage is substantially equal to the cross-over voltage to maintain near constant transconductance (gm) across the common-mode input voltage range of the CMOS input stage circuit.

1 more element

Dependencies are inferred from the claim text.

CMOS input stage circuits and related methods

Life of this patent

CMOS input stage circuits and related methods

Life of this patent

Abstract

Claims21