Input buffer with impedance cancellation
AssigneeAnalog Devices, Inc.
InventorGregory Patterson
Life of this patent
Estimating the term…
Abstract
An exemplary negative impedance converting circuit for functioning as a voltage buffer and/or negating the impedance of a connected load. The negative impedance converting circuit includes inputs, outputs, a first transconductance stage and a second transconductance stage. The transconductance gain value of the first transconductance stage is greater than a transconductance gain value of the second transconductance stage. Exemplary embodiments of a reference voltage buffer using the negative impedance converting circuit are also described.
Claims18
An input common-mode reference buffer, comprising:
- a voltage amplifier including an input for receiving a voltage reference and an output of which is connected to a gate of a first transistor and a gate of a second transistor,
- a current mirror having connection points, one connection point connected to a drain of the first transistor and another connection point connected to a drain of the second transistor, wherein the first transistor is sized to have a larger transconductance than the second transistor,
- an offset resistor connected between the drain of the first transistor and the respective connection point of the first transistor to the current mirror;
- a first feedback path to the voltage amplifier comprising the first transistor and the offset resistor,
- a second feedback path to the voltage amplifier comprising the second transistor and the current mirror;
- and
- a connection point for outputting a stable reference voltage based on the voltage applied to the input.
An input voltage buffer, comprising:
- an input connected to a first input of a voltage amplifier;
- a first feedback path including the voltage amplifier, a first transistor, and an offset resistor, wherein the first feedback path is traced from the output of the voltage amplifier through the first transistor through the offset resistor to a second input of the voltage amplifier;
- a second feedback path including the voltage amplifier, a second transistor, and a current mirror, the second feedback path tracing a path from the output of the voltage amplifier through the second transistor to a connection point on the current mirror and from another connection point on the current mirror to a second input of the voltage amplifier;
- and
- a buffer output connected at the drain of the first transistor in the first feedback path.
An amplifier circuit comprising:
- a pair of differential signal paths, each having an input terminal for a respective input voltage and an output terminal for a respective output voltage, each signal path traversing at least one respective transistor across base to emitter terminals thereof;
- an amplifier having an input for a common mode voltage and an output coupled to bases of each of the transistors via respective impedance devices,
- wherein the amplifier provides an effective output impedance having a negative impedance value.
Dependencies are inferred from the claim text.