CMOS output stage for providing stable quiescent current
First Claim
Patent Images
1. A CMOS output stage, comprising:
- a complementary transistor pair including a first MOS power transistor and a second MOS power transistor each having a drain terminal, the pair connected between a power supply line and a ground, an output of the stage being formed at the drain terminals of the first and second transistors;
a circuit connected to a gate terminal of the first MOS power transistor for setting a quiescent current of the output stage, the circuit including;
a reference source having a reference current and including a reference transistor; and
a current mirror;
an additional MOS transistor connected to the current mirror; and
a resistor connected between the additional MOS transistor and the ground,wherein the quiescent current is set by a channel geometry ratio of the second MOS power transistor and the reference transistor multiplied by the reference current, the second MOS power transistor being of the N-channel type.
1 Assignment
0 Petitions
Accused Products
Abstract
A CMOS output stage for providing stable quiescent current. The output stage includes a circuit that relates the quiescent current to the channel geometry of a power NMOS transistor and of an NMOS reference transistor of a reference current source. This configuration removes the dependency of the quiescent current on a power PMOS transistor used in the CMOS output stage, the threshold voltage of which may drift over time under high current and voltage operation, and adversely affects quiescent current stability.
-
Citations
15 Claims
-
1. A CMOS output stage, comprising:
-
a complementary transistor pair including a first MOS power transistor and a second MOS power transistor each having a drain terminal, the pair connected between a power supply line and a ground, an output of the stage being formed at the drain terminals of the first and second transistors; a circuit connected to a gate terminal of the first MOS power transistor for setting a quiescent current of the output stage, the circuit including; a reference source having a reference current and including a reference transistor; and a current mirror; an additional MOS transistor connected to the current mirror; and a resistor connected between the additional MOS transistor and the ground, wherein the quiescent current is set by a channel geometry ratio of the second MOS power transistor and the reference transistor multiplied by the reference current, the second MOS power transistor being of the N-channel type. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
-
9. A CMOS output stage comprising:
-
a complimentary pair of transistors including first and second transistors; a reference source coupled to a gate terminal of the second transistor; and a mirror circuit, coupled to the gate terminal of the second transistor, to set a quiescent current in the complimentary pair based on the first transistor and the reference source, the mirror circuit including; a current mirror having a reference input and an output connected to the gate terminal of the second transistor; an auxiliary transistor to receive an input signal to the CMOS output stage, the auxiliary transistor connected to the reference input of the current mirror and to a gate terminal of the first transistor; and a sampling element connected to the auxiliary transistor and to the gate terminal of the first transistor. - View Dependent Claims (10, 11, 12, 13)
-
-
14. A method for providing a stable quiescent current in a CMOS output stage, comprising steps of:
-
providing a reference current derived from a gate-source voltage of a reference transistor and a value of a sampling element, the reference transistor having a threshold voltage equal to that of a first transistor of a pair of complimentary output transistors; reproducing the reference current in the sampling element to generate the gate-source voltage; and applying the gate-source voltage to the first transistor to provide the quiescent current. - View Dependent Claims (15)
-
Specification