US 5,825,228 AGranted

Low quiescent power, high output power rail-to rail amplifier output stages and methods for using same

AssigneeLinear Technology Corporation

InventorWilliam H. Gross

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Abstract

Low quiescent power, high output power, rail-to-rail output stage circuits and methods are provided. The output stages are capable of providing output voltages that are substantially equal to the supply voltages (i.e., within one V.sub.CE SAT of both supply voltages) without a substantial increase in output circuit complexity and without a substantial increase in quiescent current. The output stages operate by providing a direct path for the drive signal to the output sinking transistor, and an additional, separate path for the drive signal to the output sourcing transistor. The sinking and sourcing paths are separated by a PNP transistor that gradually turns off during sinking to isolate that portion of the circuit so that the drive current to the sinking transistor is not reduced. Additional embodiments are provided where additional components are utilized to further increase the maximum sink and source currents without a significant increase in quiescent current or reduction in output swing.

Claims13

Dependent claims

An amplifier output stage comprising:

an input node that receives an input drive signal;
an output node;
a sourcing circuit coupled to a positive voltage supply, to said output node and to said input node, said sourcing circuit providing current to said output node in response to a signal representing said drive signal;
a sinking circuit coupled to a negative voltage supply, to said output node and directly connected to said input node, said sinking circuit removing current from said output node in response to said drive signal;
an isolation circuit coupled between said input node and said sourcing circuit such that substantially no drive signal goes to said sourcing circuit when said drive signal indicates that said output stage is to sink current from said output node, and such that substantially no drive signal passes through said sinking circuit when said drive signal indicates that said output stage is to source current to said output node, said isolation circuit producing said signal representing said drive signal from the drive signal when said drive signal indicates that said output stage is to source current to said output node;
said sourcing circuit comprising a sourcing output transistor coupled to said output node, said sourcing transistor having a base coupled to said input node through said isolation circuit;
and
said sinking circuit comprising a sinking output transistor coupled to said output node, said sinking transistor having a base directly coupled to said input node;
wherein said sourcing circuit further comprises:
an inversion circuit coupled to said isolation circuit;
and
a level shifting circuit coupled to said inversion circuit and to said sourcing output transistor, said level shifting circuit providing increased gain to said signal representing said drive signal.

9 more elements

An amplifier output stage comprising:

an input node that receives an input drive signal;
an output node;
a sourcing circuit coupled to a positive voltage supply, to said output node and to said input node, said sourcing circuit providing current to said output node in response to a signal representing said drive signal;
a sinking circuit coupled to a negative voltage supply, to said output node and directly connected to said input node, said sinking circuit removing current from said output node in response to said drive signal;
and
an isolation circuit coupled between said input node and said sourcing circuit such that substantially no drive signal goes to said sourcing circuit when said drive signal indicates that said output stage is to sink current from said output node, and such that substantially no drive signal passes through said sinking circuit when said drive signal indicates that said output stage is to source current to said output node, said isolation circuit producing said signal representing said drive signal from the drive signal when said drive signal indicates that said output stage is to source current to said output node wherein:
said sourcing circuit comprises a sourcing output transistor coupled to said output node, said sourcing transistor having a base coupled to said input node through said isolation circuit;
and
said sinking circuit comprises a sinking output transistor coupled to said output node, said sinking transistor having a base directly coupled to said input node wherein said isolation circuit includes a transistor having a base coupled to said input node and to said sinking output transistor wherein said sourcing output transistor includes a PNP transistor, said sinking transistor includes an NPN transistor and said isolation transistor includes a PNP transistor, said sourcing circuit further including:
an inversion circuit coupled to said isolation circuit;
and
a level shifting circuit coupled to said inversion circuit and to said sourcing output transistor, said level shifting circuit providing increased gain to said signal representing said drive signal, said amplifier output stage further comprising a cross-over distortion protection circuit coupled between said positive voltage supply and said inversion circuit, said protection circuit preventing said inversion circuit from saturating when said output stage is sinking current.

9 more elements

An amplifier output stage comprising:

an input node that receives an input drive signal;
an output node;
a sourcing circuit coupled to a positive voltage supply, to said output node and to said input node, said sourcing circuit providing current to said output node in response to a signal representing said drive signal;
a sinking circuit coupled to a negative voltage supply, to said output node and directly connected to said input node, said sinking circuit removing current from said output node in response to said drive signal;
and
an isolation circuit coupled between said input node and said sourcing circuit such that substantially no drive signal goes to said sourcing circuit when said drive signal indicates that said output stage is to sink current from said output node, and such that substantially no drive signal passes through said sinking circuit when said drive signal indicates that said output stage is to source current to said output node, said isolation circuit producing said signal representing said drive signal from the drive signal when said drive signal indicates that said output stage is to source current to said output node wherein:
said sourcing circuit comprises a sourcing output transistor coupled to said output node, said sourcing transistor having a base coupled to said input node through said isolation circuit;
and
said sinking circuit comprises a sinking output transistor coupled to said output node, said sinking transistor having a base directly coupled to said input node wherein said isolation circuit includes a transistor having a base coupled to said input node and to said sinking output transistor wherein said sourcing output transistor includes a PNP transistor, said sinking transistor includes an NPN transistor and said isolation transistor includes a PNP transistor, said sourcing circuit further including:
an inversion circuit coupled to said isolation circuit;
and
a level shifting circuit coupled to said inversion circuit and to said sourcing output transistor, said level shifting circuit providing increased gain to said signal representing said drive signal, said amplifier output stage further comprising an overdrive protection circuit coupled between said level shifting circuit and said output node so that said output node is connected in parallel with said level shifting circuit, said protection circuit preventing excess overdrive when the output of said output stage is hitting a rail voltage of one of said positive and negative voltage supplies.

9 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/592,976Filed 29 Jan 1996
Granted: 20 Oct 1998
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

H03K 17/667
The output circuit comprising more than one controlled bipolar transistor: using complementary bipolar transistors
H03F 3/3067
The collectors of complementary power transistors being connected to the output: with asymmetrical driving of the end stage
H03F 2203/45094
Indexing scheme relating to differential amplifiers: the dif amp being realized by coupling the emitters respectively sources of two common…
H03F 2203/45232
Indexing scheme relating to differential amplifiers: two dif amps of the folded cascode type are paralleled at their input gates or bases