Circuit for increasing voltage gain

Claim 2

An operational amplifier, comprising: a voltage input; a voltage gain stage having an input connected to said voltage input, a first voltage output and an output impedance; a buffer stage connected between said first voltage output and a second voltage output; and feedback means, connected between said second voltage output and said voltage gain stage, for supplying to said voltage gain stage a current which varies in proportion to voltage variations at said first voltage output to effectively increase said output impedance of said voltage gain stage.

Claim 3

An operational amplifier according to claim 1, wherein said feedback means includes a feedback device having at least three terminals, including a first terminal connected to said second voltage output, a second terminal connected to said voltage gain stage and a feedback control terminal connected to a control voltage source.

Claim 4

An operational amplifier according to claim 2, wherein said feedback device includes a transistor having a collector connected to said first terminal, an emitter connected to said second terminal and a base connected to said control terminal.

Claim 5

An operational amplifier comprising: a voltage input; a voltage gain stage having an input connected to said voltage input, a first voltage output and an output impedance, said voltage gain stage including an output device having at least three terminals, including a first terminal connected to said first voltage output, a second terminal connected by an impedance to a reference potential, and a control terminal connected to a first voltage source; a buffer stage connected between said first voltage output and a second voltage output; and feedback means, connected between said second voltage output and said second terminal of said voltage gain stage output device, for supplying to said second terminal a current which changes in proportion to voltage changes occurring at said first voltage output to effectively increase said output impedance of said voltage gain stage.

Claim 6

An operational amplifier comprising: a voltage input; a voltage gain stage having an input connected to said voltage input, a first voltage output and an output impedance, said voltage gain stage including an output device having at least three terminals, including a first terminal connected to said first voltage output, a second terminal connected by an impedance to a reference potential, and a control terminal connected to a first voltage source; a buffer stage connected between said first voltage output and a second voltage output; and feedback means, connected between said second voltage output and said second terminal of said voltage gain stage output device, for supplying to said second terminal a current which changes in proportion to voltage changes occurring at said first voltage output to effectively increase said output impedance of said voltage gain stage.

Claim 7

An operational amplifier according to claim 4, wherein said feedback means includes a feedback device having at least three terminals, including a first terminal connected to said second voltage output, a second terminal connected to said second terminal of said voltage gain stage output device, and a control terminal connected to a second voltage source.

Claim 8

An operational amplifier according to claim 5, wherein said first voltage source and said second voltage source provide voltage levels which are substantially equivalent.

Claim 9

An operational amplifier according to claim 5, wherein said voltage gain stage output device and said feedback device are a matched pair.

Claim 10

An operational amplifier according to claim 5, wherein said feedback device includes a transistor having a collector connected to said first terminal, an emitter connected to said second terminal and a base connected to said control terminal.

Claim 11

An operational amplifier according to claim 8, wherein said voltage gain stage output device includes a transistor having a collector connected to said first terminal, an emitter connected to said second terminal and a base connected to said output control terminal.

Claim 12

An operational amplifier according to claim 9, wherein said output device transistor and said feedback device transistor are a matched pair.

Claim 13

An operational amplifier, comprising: a voltage input; a voltage gain stage having an input connected to said voltage input, and having a first voltage output, and having an output transistor connected in a common-emitter configuration, said transistor having a collector connected to a current source and to said first voltage output, an emitter connected by an impedance to a reference potential, and a base connected to a first control voltage; a buffer stage connected between said first voltage output and a second voltage output; and a feedback device having a first terminal connected to said second voltage output, a second terminal connected to said emitter of said output transistor and a control terminal connected to a second control voltage.

Claim 14

An operational amplifier, comprising: a voltage input; a voltage gain stage having an input connected to said voltage input, and having a first voltage output, and having an output transistor connected in a common-emitter configuration, said transistor having a collector connected to a current source and to said first voltage output, an emitter connected by an impedance to a reference potential, and a base connected to a first control voltage; a buffer stage connected between said first voltage output and a second voltage output; and a feedback device having a first terminal connected to said second voltage output, a second terminal connected to said emitter of said output transistor and a control terminal connected to a second control voltage.

Claim 15

An operational amplifier according to claim 11, wherein said feedback device is a transistor having a collector connected to said first terminal, an emitter connected to said second terminal, and a base connected to said second control voltage.

Claim 16

An operational amplifier according to claim 12, wherein said transistors are a matched pair.

Claim 17

An operational amplifier according to claim 12, wherein said first control voltage is substantially equal to said second control voltage.

Claim 18

An operational amplifier, comprising: a voltage input; a voltage gain stage having an input connected to said voltage input, and having a first voltage output, and having an output transistor connected in a common-source configuration, said transistor having a drain connected to a current source and to said first voltage output, a source connected by an impedance to a reference potential, and a gate connected to a first control voltage; a buffer stage connected between said first voltage output and a second voltage output; and a feedback device having a first terminal connected to said second voltage output, a second terminal connected to said source of said output transistor and a control terminal connected to a second control voltage.

Claim 19

An operational amplifier, comprising: a voltage input; a voltage gain stage having an input connected to said voltage input, and having a first voltage output, and having an output transistor connected in a common-source configuration, said transistor having a drain connected to a current source and to said first voltage output, a source connected by an impedance to a reference potential, and a gate connected to a first control voltage; a buffer stage connected between said first voltage output and a second voltage output; and a feedback device having a first terminal connected to said second voltage output, a second terminal connected to said source of said output transistor and a control terminal connected to a second control voltage.

Claim 20

An operational amplifier according to claim 15, wherein said feedback device is a transistor having a drain connected to said first terminal, a source connected to said second terminal, and a gate connected to said second control voltage.

Claim 21

An operational amplifier according to claim 16, wherein said transistors are a matched pair.

Claim 22

An operational amplifier according to claim 16, wherein said first control voltage is substantially equal to said second control voltage.