US 7,002,422 B1 · Current-mirrored crystal-oscillator circuit without feedback to reduce power consumption

Abstract

An oscillator inverter circuit has an input at a first crystal node and drives a second crystal node of a crystal oscillator. The first node is lightly loaded by a gate of an input transistor that generates a buffered node. The buffered node voltage is converted to a varying current by a converter transistor. Another varying current through upper and lower amplifier transistors are mirrored to upper and lower current mirror transistors. The gate and drain of the lower current mirror transistor are connected to the gate of an output transistor that pulls down the second node with low impedance. The drain of the upper current mirror transistor diverts current from an output current source, changing pull-up current to the second node through a p-channel transistor. An input resistor between the first node and the buffered node provides a DC bias but blocks AC oscillation signals.

Claims20

Dependent claims

An oscillator inverter circuit comprising:

a first crystal node and a second crystal node that are for coupling across a crystal oscillator;
a plurality of current sources generating source currents that are relatively insensitive to changes in a power-supply voltage including an amplifier source current and an output source current;
a low-gain input stage having a gate on the first crystal node and outputting a buffered node buffered from the first crystal node;
a gain stage having a converter transistor that receives the buffered node on a gate and generates a varying current that varies with voltage variations of the first crystal node;
a current mirror that receives a current difference of the amplifier source current and the varying current, the current mirror generating a mirrored voltage by mirroring the current difference;
and
an output stage that receives the output source current and the mirrored voltage, with an output transistor that has a gate driven by the mirrored voltage and is connected to the second crystal node,
whereby the varying current is mirrored by the current mirror to control driving of the second crystal node by the output stage.

5 more elements

A current-mirrored crystal oscillator comprising:

a crystal, coupled between a first node and a second node, that oscillates at an oscillation frequency when connected to a gain inverter;
a bias resistor coupled between the first and second nodes, for biasing the first and second nodes to an intermediate voltage;
a gain inverter, having an input driven by the first node, for driving the second node to induce oscillation by the crystal, wherein the gain inverter comprises:
an input transistor having a gate connected to the first node and a drain driving a buffered node;
a converter transistor having a gate connected to the buffered node, for generating a varying current that varies with small-signal variations on the first node;
a current mirror, coupled to mirror changes in the varying current to generate a mirrored node;
and
an output stage, responsive to the mirrored node, for driving an output current from the second node,
whereby the small-signal variations on the first node are buffered, converted to the varying current, and mirrored to drive the output current from the second node.

6 more elements

Dependencies are inferred from the claim text.

Current-mirrored crystal-oscillator circuit without feedback to reduce power consumption

Life of this patent

Current-mirrored crystal-oscillator circuit without feedback to reduce power consumption

Life of this patent

Abstract

Claims20