Tail current generator circuit for bipolar/MOS differential pair to set precise transconductance
AssigneeTexas Instruments Incorporated
InventorJohn Joseph Price, Jr.
Life of this patent
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Abstract
Disclosed is a circuit and method for generating a tail current for a main reader amplifier (200) input stage using a scaled master differential stage (160) with a given offset to force a given output current, preceded by a balanced stage (150) to get a balanced offset. Current must be set by a feedback arrangement in the dummy master stage (160) which is a scaled version of the main reader amplifier input stage (200). The current derived in the dummy master stage (160), when appropriately scaled and used as the tail current of the main reader amplifier (200) input stage provides a precisely controlled gain.
Claims23
A circuit adapted to generate a tail current for a main amplifier stage, comprising:
- a master stage circuit;
- a balanced stage circuit;
- master stage circuit responsively coupled to the balanced stage circuit,
- the master stage having a predetermined offset operable to force a given tail current to the balanced stage circuit and a main reader amplifier;
- and
- the balanced stage circuit comprising at least one bi-polar and MOS transistor differential pair adapted to provide a balanced offset to the master stage circuit.
Bias circuitry for a reader amplifier, comprising:
- a master transconductance (gm) stage configured as a scaled reader amplifier;
- a balanced stage circuit;
- and
- the scaled reader amplifier responsively coupled to the balanced stage circuit,
- the scaled reader amplifier operable to provide a tail current for the balanced stage circuit and a reader amplifier.
A circuit arrangement for providing a tail current to an amplifier, comprising:
- a scaled master differential stage;
- a balanced stage circuit comprising at least one bi-polar and MOS transistor differential pair adapted to provide a balanced offset to the scaled master differential stage;
- the scaled master differential stage having a given offset adapted to force a given tail current.
A tail current generator circuit, comprising:
- a master transconductance stage;
- a balanced offset stage including at least one bipolar-MOS differential transistor pair adapted to provide a balanced offset to the master transconductance stage;
- the master transconductance stage adapted to set a precise transconductance of the bipolar-MOS differential transistor pair;
- and
- the tail current generator circuit responsive to the master transconductance stage and operable to provide an output which matches an absolute current as a function of a predetermined voltage input offset.
A method of generating a tail current for an amplifier, comprising the steps of:
- adapting a differential, scaled master stage to accept a balanced offset;
- generating a current by a feedback arrangement in the differential, scaled master stage;
- scaling the current derived in the differential, scaled master stage;
- and
- providing the scaled current as the tail current for an amplifier.
Dependencies are inferred from the claim text.