Feedback systems

Claim 2

A low pass feedback amplifier system, comprising: a multi-stage amplifier constituting the forward path of the low pass feedback amplifier system, said amplifier having a plurality of stages operatively connected in cascade, said stages having respective predetermined gains, poles, and zeros; and at least two feedback networks operatively connected to said forward path to form a set of nested feedback loops, said loops being nested one within the next, each said feedback network having a predetermined transfer function in complex frequency notation of the approximate form sτ, and wherein the gains, poles and zeros of the individual stages of the forward path, and the transfer functions of the feedback networks are predetermined such that the stage or stages within the innermost of the feedback loops has a return difference which changes at a rate greater than Bode's limit for unconditional stability.

Claim 3

The feedback amplifier system of claim 1 wherein the poles and zeros of the individual stages of said forward path and the transfer functions of said feedback networks are predetermined such that each feedback loop, with all other loops enclosed by it operating, is unconditionally stable.

Claim 4

The feedback amplifier system of claim 1, wherein said feedback networks comprise LRC networks.

Claim 5

The feedback amplifier system of claim 1, further comprising an additional feedback network operatively connected to said forward path to form an additional feedback loop outside said nested feedback loops.

Claim 6

The feedback amplifier system of claim 4, wherein said additional feedback network comprises any arbitrary LRC network.

Claim 7

The feedback amplifier system of claim 4, wherein said additional feedback network comprises a simple divider network.

Claim 8

The feedback amplifier system of claim 4, wherein a portion of the forward path is included in the innermost feedback loop, said portion having two dominant poles.

Claim 9

The feedback amplifier system of claim 4, wherein a portion of the forward path is included between two adjacent differentiating feedback networks of the nest, said portion having one dominant pole and one dominant zero.

Claim 10

The feedback amplifier system of claim 8, wherein all dominant poles are coincident.

Claim 11

The feedback amplifier system of claim 8, wherein all dominant zeros are coincident.

Claim 12

The feedback amplifier system of claim 4, wherein a portion of the forward path is included between an outermost differentiating feedback loop of said nest and said additional feedback network, said portion having no significant poles or zeros.

Claim 13

The feedback amplifier system of claim 4, wherein all said differentiating feedback networks have the same time constant.

Claim 14

The feedback amplifier system of claim 1, wherein said amplifier includes a final stage comprising an output stage, said nest of feedback loops being centered on the output stage.

Claim 15

The feedback amplifier system of claim 1, wherein said amplifier includes a final stage comprising an output stage, said nested feedback loops being centered on any stage other than the output stage.

Claim 16

The feedback amplifier system of claim 1, wherein the gain around each said feedbck loop, with all other loops enclosed by it operating, rises or falls at 20 dB/decade when the magnitude of said gain around each said feedback loop is greater than unity.

Claim 17

A high pass feedback amplifier system, comprising: a multi-stage amplifier constituting the forward path of the high pass feedback amplifier system, said amplifier having a plurality of stages operatively connected in cascade, said stages having respective predetermined gains, poles, and zeros; and at least two feedback networks operatively connected to said forward path to form a set of nested feedback loops, said loops being nested one within the next, each said feedback network having a predetermined transfer function in complex frequency notation of the approximate form 1/sτ, and wherein the gains, poles and zeros of the individual stages of the forward path, and the transfer functions of the feedback networks are predetermined such that the stage or stages within the innermost of the feedback loops has a return difference which changes at a rate greater than Bode's limit for unconditional stability.

Claim 18

A high pass feedback amplifier system, comprising: a multi-stage amplifier constituting the forward path of the high pass feedback amplifier system, said amplifier having a plurality of stages operatively connected in cascade, said stages having respective predetermined gains, poles, and zeros; and at least two feedback networks operatively connected to said forward path to form a set of nested feedback loops, said loops being nested one within the next, each said feedback network having a predetermined transfer function in complex frequency notation of the approximate form 1/sτ, and wherein the gains, poles and zeros of the individual stages of the forward path, and the transfer functions of the feedback networks are predetermined such that the stage or stages within the innermost of the feedback loops has a return difference which changes at a rate greater than Bode's limit for unconditional stability.

Claim 19

The feedback amplifier system of claim 16, wherein the poles and zeros of the individual stages of said forward path and the transfer functions of said feedback networks are predetermined such that each feedback loop, with all other loops enclosed by it operating, is unconditionally stable.

Claim 20

The feedback amplifier system of claim 16, wherein said feedback networks comprise LRC networks.

Claim 21

The feedback amplifier system of claim 16, further comprising an additional feedback network operatively connected to said forward path to form an additional feedback loop outside said nest of feedback loops.

Claim 22

The feedback amplifier system of claim 19, wherein said additional feedback network comprises any arbitrary LRC network.

Claim 23

The feedback amplifier system of claim 19, wherein said additional feedback network comprises a simple divider network.

Claim 24

The feedback amplifier system of claim 16, wherein said amplifier includes a final stage comprising an output stage, said nest of feedback loops being centered on the output stage.

Claim 25

The feedback amplifier system of claim 16, wherein said amplifier includes a final stage comprising an output stage, said nest of feedback loops being centered on any stage other than the output stage.

Claim 26

The feedback amplifier system of claim 16, wherein the gain around each feedback loop, with all other loops enclosed by it operating, rises or falls at 20 dB/decade when the magnitude of said gain around each said feedback loop is greater than unity.

Claim 27

A band pass feedback amplifier system comprising: a multi-stage amplifier constituting the forward path of the band pass feedback amplifier system, said amplifier having a plurality of stages operatively connected in cascade, said stages having respective predetermined gains, poles, and zeros; and at least two feedback networks operatively connected to said forward path to form a set of nested feedback loops, said loops being nested one within the next, each said feedback network having a predetermined transfer function in complex frequency notation of the approximate form (sτ+1/sτ), and wherein the gains, poles and zeros of the individual stages of the forward path, and the transfer functions of the feedback networks are predetermined such that the stage or stages within the innermost of the feedback loops has a return difference which changes at a rate greater than Bode's limit for unconditional stability.

Claim 28

A band pass feedback amplifier system comprising: a multi-stage amplifier constituting the forward path of the band pass feedback amplifier system, said amplifier having a plurality of stages operatively connected in cascade, said stages having respective predetermined gains, poles, and zeros; and at least two feedback networks operatively connected to said forward path to form a set of nested feedback loops, said loops being nested one within the next, each said feedback network having a predetermined transfer function in complex frequency notation of the approximate form (sτ+1/sτ), and wherein the gains, poles and zeros of the individual stages of the forward path, and the transfer functions of the feedback networks are predetermined such that the stage or stages within the innermost of the feedback loops has a return difference which changes at a rate greater than Bode's limit for unconditional stability.

Claim 29

The feedback amplifier system of claim 25, wherein the poles and zeros of the individual stages of said forward path and the transfer functions of said feedback networks are predetermined such that each feedback loop, with all other loops enclosed by it operating, is unconditionally stable.

Claim 30

The feedback amplifier system of claim 25, wherein said feedback networks comprise LRC networks.

Claim 31

The feedback amplifier system of claim 25, further comprising an additional feedback network operatively connected to said forward path to form an additional feedback loop outside said nested feedback loops.

Claim 32

The feedback amplifier system of claim 28, wherein said additional feedback network comprises any arbitrary LRC network.

Claim 33

The feedback amplifier system of claim 28, wherein said additional feedback network comprises a simple divider network.

Claim 34

The feedback amplifier system of claim 25, wherein said amplifier includes a final stage comprising an output stage, said nest of feedback loops being centered on the output stage.

Claim 35

The feedback amplifier system of claim 25, wherein said amplifier includes a final stage comprising an output stage, said nested feedback loops being centered on any stage other than the output stage.

Claim 36

A band stop feedback amplifier system, comprising: a multi-stage amplifier constituting the forward path of the band stop feedback amplifier system, said amplifier having a plurality of stages operatively connected in cascade, said stages having respective predetermined gains, poles, and zeros; and at least two feedback networks connected to said forward path to form a set of nested feedback loops, said loops being nested one within the next, each said feedback network having a predetermined transfer function in complex frequency notation of the approximate form 1/(s τ+1/s τ), and wherein the gains, poles and zeros of the individual stages of the forward path, and the transfer functions of the feedback networks are predetermined such that the stage or stages within the innermost of the feedback loops has a return difference which changes at a rate greater than Bode's limit for unconditional stability.

Claim 37

A band stop feedback amplifier system, comprising: a multi-stage amplifier constituting the forward path of the band stop feedback amplifier system, said amplifier having a plurality of stages operatively connected in cascade, said stages having respective predetermined gains, poles, and zeros; and at least two feedback networks connected to said forward path to form a set of nested feedback loops, said loops being nested one within the next, each said feedback network having a predetermined transfer function in complex frequency notation of the approximate form 1/(s τ+1/s τ), and wherein the gains, poles and zeros of the individual stages of the forward path, and the transfer functions of the feedback networks are predetermined such that the stage or stages within the innermost of the feedback loops has a return difference which changes at a rate greater than Bode's limit for unconditional stability.

Claim 38

The feedback amplifier system of claim 33, wherein the poles and zeros of the individual stages of said forward path and the transfer functions of said feedback networks are predetermined such that each feedback loop; with all other loops enclosed by it operating, is unconditionally stable.

Claim 39

The feedback amplifier system of claim 34, further comprising an additional feedback network operatively connected to said forward path to form an additional feedback loop outside nested feedback loops.

Claim 40

The feedback amplifier system of claim 35, wherein said additional feedback network comprises any arbitrary LRC network.

Claim 41

The feedback amplifier system of claim 35, wherein said additional feedback network comprises a simple divider network.

Claim 42

The feedback amplifier system of claim 33, wherein said feedback networks comprise LRC networks.

Claim 43

The feedback amplifier system of claim 33, wherein said amplifier includes a final stage comprising an output stage, said nested feedback loops being centered on the output stage.

Claim 44

The feedback amplifier system of claim 33, wherein said amplifier includes a final stage comprising an output stage, said nested feedback loops being centered on any stage other than the output stage.

Claim 45

A low pass feedback amplifier system, comprising: a multi-stage low pass amplifier constituting a forward path of the low pass feedback amplifier system, said amplifier having N stages designated 1 through N operatively connected in cascade, said N stages having respective predetermined gains designated as μ1 through μN, stages 2 through N each having a dominant pole of time constant τ o , stages 2 through N-2 each having a dominant zero of time constant τ x ; a plurality of feedback networks operatively connected to said forward path to form inner and outer nested feedback loops, each said feedback loop having a predetermined transfer function in complex frequency notation of the approximate form s τ F , and each said feedback network feeding back to an input of one of stages 2 through N-1 a time derivative of an output from stage N; and an additional feedback network operatively connected to feed back a fraction β of said output from stage N to an input of stage 1, and wherein the following inter-relations apply approximately: μ.sub.k =τ.sub.0 /τ.sub.X for < K<N-2 μ.sub.1 μ.sub.N-1 μ.sub.N β=(τ.sub.0 /τ.sub.X).sup.2 τ.sub.F =μ.sub.1 βτ.sub.X.

Claim 46

A low pass feedback amplifier system, comprising: a multi-stage low pass amplifier constituting a forward path of the low pass feedback amplifier system, said amplifier having N stages designated 1 through N operatively connected in cascade, said N stages having respective predetermined gains designated as μ1 through μN, stages 2 through N each having a dominant pole of time constant τ o , stages 2 through N-2 each having a dominant zero of time constant τ x ; a plurality of feedback networks operatively connected to said forward path to form inner and outer nested feedback loops, each said feedback loop having a predetermined transfer function in complex frequency notation of the approximate form s τ F , and each said feedback network feeding back to an input of one of stages 2 through N-1 a time derivative of an output from stage N; and an additional feedback network operatively connected to feed back a fraction β of said output from stage N to an input of stage 1, and wherein the following inter-relations apply approximately: μ.sub.k =τ.sub.0 /τ.sub.X for < K<N-2 μ.sub.1 μ.sub.N-1 μ.sub.N β=(τ.sub.0 /τ.sub.X).sup.2 τ.sub.F =μ.sub.1 βτ.sub.X.

Claim 47

The feedback amplifier system of claim 41, wherein said plurality of feedback networks comprise LRC networks.