United States Patent 1191
`Westmoreland
`
`[54] OPERATIONAL AMPLIFIER WITH
`DIGITALLY PROGRAMMABLE GAIN
`CIRCUITRY ON THE SAME CHIP
`[75] Inventor:
`John C. Westmoreland, Stafford,
`Tex.
`[73] Assignee: Texas Instruments Incorporated,
`Dallas, Tex.
`Appl. No.: 4,827
`Filed:
`Jan. 15, 1993
`
`[21]
`[22]
`[5 1]
`[52]
`[58]
`[56]
`
`Int. Cl.5 ............................................. .. H03G 3/30
`
`US. Cl. . . . . a . . . . . . . . . . . . .
`
`. . . . .. 330/282; 330/86
`
`Field of Search ................................ .. 330/86, 282
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,500,845 2/l985 Ehni .................................... .. 330/86
`5,233,309 8/1993 Spitalny et al. ............... .. 330/282 X
`
`FOREIGN PATENT DOCUMENTS
`
`58306 5/1981 Japan ................................. .. 330/282
`60810 4/1983 Japan
`...... .. 330/282
`37716 3/1984 Japan
`...... .. 330/282
`96413 4/1990 Japan ................................. .. 330/282
`
`lllllllllllllllllllllllllllIHIIIIIIIIllllIllllllllllllllllllllllllllllllll
`5,325,071
`Jun. 28, 1994
`
`[11]
`[45]
`
`Patent Number:
`Date of Patent:
`
`' USOO5325071A
`
`Primary Examiner-James B. Mullins
`Attorney, Agent, or Firm-Wade James Brady; Richard
`L. Donaldson
`ABSTRACT
`[57]
`A single chip operational ampli?er wherein the gain is
`programmable by means of a digitally controlled feed
`back loop wherein the parameters of the feedback cir
`cuit are digitally programmable under control of a mi~
`croprocessor, microcontroller, control logic and the
`like. There is provided an operational ampli?er with a
`feedback loop from output terminal to input terminal.
`The feedback loop contains components which are
`switched into the feedback loop circuit under control of
`digital signal provided by an external device, such as,
`for example, a microprocessor, microcontroller, control
`logic and the like. The digital signals from the external
`device cause the appropriate resistors and/or capacitors
`and/or other components, as may be required, to be
`switched into the feedback loop of the operational am
`pli?er to provide the desired gain. These digital signals
`can be derived from a monitoring source which is de
`signed to provide automatic gain control (AGC) or the
`.
`111“
`
`8Claims, 1 Drawing Sheet
`
`: DIGITAL N5
`75 ___ CONTROL
`—-— CIRCUITRY
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`3
`
`Samsung Electronics Co., Ltd., et al.
`Ex. 1013, p. 1
`
`LG Exhibit 1013, Page 1
`LG Electronics, Inc. v. Papst Licensing
`
`

`

`US. Patent
`
`June 28,1994
`
`5,325,071
`
`—-— DIGITAL N
`
`5
`
`__ CIRCUITRY
`
`75 {:1 CONTROL
`5
`l
`COMPONENT A/
`73 H 7 [STORAGE 1
`I
`Fig. I
`
`9
`
`SELECTO SELECT1 SELECTN
`NMOS
`PASS
`GATE 2 7
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`
`23
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`
`Fig. 2
`
`Samsung Electronics Co., Ltd., et al.
`Ex. 1013, p. 2
`
`LG Exhibit 1013, Page 2
`LG Electronics, Inc. v. Papst Licensing
`
`

`

`1
`
`5,325,071
`
`'
`
`OPERATIONAL AMPLIFIER WITH DIGITALLY
`PROGRAMMABLE GAIN CIRCUITRY ON THE
`SAME CHIP
`
`10
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`This invention relates to operational ampli?ers and,
`more speci?cally, to an operational ampli?er having
`selectively programmable digitally operated gain cir
`cuitry on the same chip.
`2. Brief Description of the Prior Art
`Programmable operational ampli?ers in accordance
`with the prior art have typically been programmed with
`resistor selection that requires a physical change to the
`circuitry involved, the resistors being disposed external
`to the chip containing the ampli?er circuitry. In such
`prior art programmable operational ampli?ers, current
`has been passed through a resistor that must be physi
`cally changed in the circuit to change the gain of the
`ampli?er. The major problem with this approach is that
`the resistors are selected in a non-programmable man
`ner external to the chip containing the operational am
`pli?er. It is desired to provide the same type of function
`on a single chip.
`
`20
`
`25
`
`2
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`Referring to FIG. 1, there is shown a standard opera
`tional ampli?er 1 having an input terminal 7 and an
`output terminal 9. The operational ampli?er 1 as shown
`has the input terminal 7 connected to the non-inverting
`(+) input with the other (—) input grounded. A feed
`back circuit 3 is connected between the ampli?er output
`terminal 9 and the ampli?er input terminal 7, the feed
`back circuit being a component store under control of
`the digital control circuitry 5 to provide a selected
`parameter value composed of resistors and/or capaci
`tors and/or other components to provide a desired gain
`in the ampli?er circuit. A resistor 11 is coupled in series
`with the circuit input 13 and the ampli?er input terminal
`7.
`The component store 3 is a collection of resistors of
`various values and/or capacitors of various values and
`/or other components which are connectable together
`in one of a plurality of circuit con?gurations as deter
`mined by and under control of the digital control cir
`cuitry 5. The components in component store 3 are
`switched into and out of the circuit.
`The digital control circuitry 5 has a plurality of inputs
`15 which receive a binary signal from an external digital
`source, such as a microprocessor, microcomputer,
`logic, etc.
`The circuitry of the component store 3 and the digital
`control circuitry 5 are shown in FIG. 2 wherein resis
`tors R0, R1 and RN are shown, each of these resistors
`being coupled to an input which is also the input to
`ampli?er 1 via an associated switch shown as transistors
`21, 23 and 25 respectively. Each of the resistors R0, R1
`and R Nis coupled to the output which is also the output
`of ampli?er 1 via an associated switch shown as transis
`tors 27, 29 and 31‘respectively. Resistors R0 and R1, R1
`and R2 or R0, R1 and R; can be placed in the circuit by
`appropriate operation of switches 27, 29 and 31 and
`switches 33 and 35 which connect together the resistors
`in a series con?guration. The resistors Ra, R1...RN,
`though shown as resistors, can also be capacitors or RC
`combinations.
`In operation, for example, to select resistor R0 only,
`the transistors 21 and 27 are turned on or are in the “1"
`state by selection of control elements Selecto and Cute
`with all other switches being in the “0" state. To select
`resistor R1 in parallel with resistor R0, transistors 21, 23,
`27 and'29 are in the “1” state with all other transistors
`being in the “0” state. To select resistor Rain series with
`resistor R1, transistors 21, 33 and 29 are in the “l” state
`and all other transistors are in the “0” state. To operate
`as an automatic gain control (AGC), the processor,
`controller, etc. continually looks at the output 9 via a
`voltage sensor to determine which select and control
`lines to enable to maintain the output voltage at the
`desired level.
`The circuitry as set forth hereinabove is adaptable for
`placement in its entirety on a single semiconductor chip
`by use of LinBCMOS that includes both the bipolar and
`PET input circuitry of the operational ampli?er and the
`CMOS digital control circuitry.
`In operation, digital signals will be received at the
`inputs 15 of the digital control circuitry 5 and select the
`appropriate components in the component storage 3
`which are required to provide the needed gain and
`connection thereof in a speci?ed circuit arrangement as
`explained hereinabove.
`
`SUMMARY OF THE INVENTION
`In accordance with the present invention, the above
`described problem of the prior art is eliminated and
`there is provided an operational ampli?er wherein the
`gain is programmable by means of a digitally controlled
`feedback loop wherein the parameters of the feedback
`circuit are digitally programmable under control of a
`microprocessor, microcontroller, control logic and the
`like and all components are disposed on a single chip.
`This provides a saving of space, a reduction in noise and
`a reduction in cost since both the board size and compo
`nent count are also reduced.
`Brie?y, there is provided an operational ampli?er
`with an on-chip component storage which provides the
`feedback loop from output terminal to input terminal.
`The feedback loop contains on-chip external compo
`nents which are switched into the feedback loop circuit
`under control of digital signals provided by an external
`device, such as, for example, a microprocessor, mi
`crocontroller, control logic and the like. The digital
`signals from the external device cause the appropriate
`resistors and/ or capacitors and/ or other components, as
`may be required, in the on-chip component storage to
`be switched into the feedback loop of the operational
`ampli?er to provide the desired gain. These digital sig
`nals can be derived from a monitoring source which is
`designed to provide automatic gain control (AGC) or
`the like.
`
`30
`
`35
`
`45
`
`50
`
`55
`
`BRIEF DESCRIPTION OF THE DRAWING
`FIG. 1 is a block diagram of an operational ampli?er
`with digitally controlled circuitry in the feedback loop
`thereof for controlling component parameter content
`and arrangement in the feedback loop of the ampli?er;
`and
`FIG. 2 is a circuit diagram of the digital control cir
`cuitry and external components controlled therewith of
`FIG. 1.
`
`65
`
`Samsung Electronics Co., Ltd., et al.
`Ex. 1013, p. 3
`
`LG Exhibit 1013, Page 3
`LG Electronics, Inc. v. Papst Licensing
`
`

`

`5,325,071
`
`3
`The system can operate as an automatic gain control
`by continually updating the digital signals at the input
`15 to provide the desired ampli?er gain on line as ex
`plained hereinabove.
`Though the invention has been described with re
`spect to a speci?c preferred embodiment thereof, many
`variations and modi?cations will immediately become
`apparent to those skilled in the art. It is therefore the
`intention that the appended claims be interpreted as
`broadly as possible in view of the prior art to include all
`such variations and modi?cations.
`I claim:
`1. An ampli?er circuit on a single semiconductor chip
`which comprises:
`(a) a semiconductor chip having thereon each of:
`(i) an ampli?er having an input terminal and an
`output terminal;
`(ii) a digitally operated control circuit; and
`(iii) a feedback circuit disposed between said input
`terminal and said output terminal ,said feedback
`circuit including a plurality of electrical circuit
`components, each of said circuit components
`having an upstream terminus and a downstream
`terminus, each of said circuit components having
`associated therewith a separate first series con
`nected switch controlled by said control circuit
`and coupled to the upstream terminus of said
`
`4
`electrical component and a separate second se
`ries connected switch controlled by said control
`circuit and coupled to the downstream terminus
`of said electrical circuit component, and a plural
`ity of separate switches controlled by said con
`trol circuit, each of said separate switches cou
`pled between the downstream terminus of an
`associated one of said circuit components and
`the upstream terminus of a different one of the
`other circuit components to provide intercon
`nection of said circuit components on-line in one
`of plural serial and parallel arrangements.
`2. The circuit of claim 1 wherein said ampli?er is an
`operational ampli?er.
`3. The circuit of claim 2 further including an electri
`cally resistive element coupled to said input terminal.
`4. The circuit of claim 3 wherein said digitally oper
`ated control circuit is programmable.
`5. The circuit of claim 2 wherein said digitally oper
`ated control circuit is programmable.
`6. The circuit of claim 1 further including an electri
`cally resistive element coupled to said input terminal.
`7. The circuit of claim 6 wherein said digitally oper
`ated control circuit is programmable.
`8. The circuit of claim 1 wherein said digitally oper
`ated control circuit is programmable.
`& 1
`$ ' i
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`20
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`25
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`35
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`45
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`50
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`55
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`65
`
`Samsung Electronics Co., Ltd., et al.
`Ex. 1013, p. 4
`
`LG Exhibit 1013, Page 4
`LG Electronics, Inc. v. Papst Licensing
`
`