Quiescent current control for the output stage of an amplifier
AssigneeLucent Technologies Inc.
InventorMilton Luther Embree
Life of this patent
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Abstract
The invention is an amplifier such as an operational amplifier having an output stage with a reduced quiescent current control transistor device area that provides sufficient quiescent current control for proper operation thereof. The output stage includes a current diverter or diverting arrangement whereby current flowing to the quiescent current control transistor area is reduced by diversion without jeopardizing the proper operation of the operational amplifier. In this manner, the relative size of the quiescent current control transistors can be significantly reduced without sacrificing any of the overall performance of the amplifier.
Claims14
An integrated circuit having an amplifier with an output stage, said output stage for use with a constant current source, said output stage comprising:
- an output side having at least one drive transistor;
- and
- a quiescent current control side through which substantially all of the current from said constant current source flows, said quiescent current control side operably connected to said output side in such a way that causes a quiescent current flowing through said output side to be maintained at a value that is substantially proportional to the current that flows through said quiescent current control side,
- said quiescent current control side having
- a quiescent current control section including at least one control transistor, said quiescent current control section connected to said output side in such a way as to maintain quiescent current within said output stage at said value notwithstanding changes in temperature, and
- a current diverter operably connected to said quiescent current control section that alters current flow through said quiescent current control section in such a way that allows said quiescent current control side to be fabricated with transistors having characteristic sizes that are substantially smaller than the characteristic size of said at least one output side drive transistor, said current diverter including
- a first current diverter branch having a first amplifying transistor, said first branch operably coupled to said control transistor in such a way that causes at least a portion of the current flowing from said constant current source to flow through said first branch in such a way that the amount of current flowing through said first branch as compared to that flowing through said control transistor is related to the characteristic size of said first amplifying transistor as compared to the characteristic size of said control transistor, and
- a second current diverter branch having a second amplifying transistor, said second branch operably coupled to said first branch in such a way that causes at least a portion of the current flowing from said constant current source to flow through said second branch in such a way that the amount of current flowing through said second branch is related to the characteristic size of said second amplifying transistor.
An integrated circuit having an amplifier, said amplifier for use with a positive source voltage and a negative source voltage, said amplifier comprising:
- a first stage having a noninverting input, an inverting input, an output and a constant current source, said first stage connected between said positive and negative source voltages;
- and
- an output stage having
- an output side having a positive output drive transistor connected to said positive source voltage and a negative output drive transistor connected to said negative source voltage,
- a quiescent current control side through which substantially all of the current from said constant current source flows, said quiescent current control side operably connected to said output side in such a way that causes a quiescent current flowing through said output side to be maintained at a value that is substantially proportional to the current that flows through said quiescent current control side, said quiescent current control side having a pair of diode-connected control transistors and a current diverter,
- said diode-connected control transistors being operably connected to said output side in such a way that maintains quiescent current within said output stage at said value notwithstanding changes in temperature, and
- said current diverter being operably connected to said diode-connected control transistors and said output side to alter current flow from said constant current source through said diode-connected control transistors in such a way that allows said diode-connected control transistors to have characteristic sizes that are substantially smaller than the characteristic sizes of said output side drive transistors.
Dependencies are inferred from the claim text.