Electronically controlled variable resistance device

Claim 2

An electronically controlled variable impedance device comprising: a plurality of electrical circuit branches connected in parallel, at least certain ones of said branches each including a controllable impedance element and an element providing a preselected fixed impedance connected in series; and a plurality of control amplifier means responsive to a common master control voltage and having respective outputs coupled to respective ones of said controllable impedance elements for providing a variable control voltage for the associatEd controllable impedance element over a preselected range of said master control voltage and for providing a first essentially constant control voltage for said controllable impedance element in response to a master control voltage below said preselected range and a second essentially constant control voltage for said controllable impedance element in response to a master control voltage above said preselected range, said first essentially constant control voltage being of a value to render said associated controllable impedance element heavily conductive of current, said second essentially constant control voltage being of a value to render said associated controllable impedance element essentially nonconductive of current, and said variable control voltage being in a range to render said associated controllable impedance element conductive of current at an intermediate level determined by the value of said master control voltage.

Claim 3

An electronically controlled variable resistance device comprising: a first resistor providing a preselected resistance and connected between first and second terminals; a plurality of electrical circuit branches connected in parallel with said first resistor between said first and second terminals, each of said branches including a resistor providing a predetermined fixed resistance and a controllable resistance element connected in series; and a plurality of control amplifier means responsive to a common master control voltage and having respective outputs coupled to respective ones of said controllable resistance elements for providing a variable control voltage for the associated controllable resistance element over a preselected range of said master control voltage and for providing a first essentially constant control voltage for said controllable resistance element in response to a master control voltage below said preselected range and a second essentially constant control voltage for said controllable resistance element in response to a master control voltage above said preselected range, said first essentially constant control voltage being of a value to render said associated controllable resistance element heavily conductive of current, said second essentially constant control voltage being of a value to render said associated controllable resistance element essentially nonconductive of current, and said variable control voltage being in a range to render said associated controllable resistance element conductive of current at an intermediate level determined by the value of said master control voltage.

Claim 4

An electronically controlled variable resistance device comprising: a first resistor providing a preselected resistance and connected between first and second terminals; a plurality of electrical circuit branches connected in parallel with said first resistor between said first and second terminals, each of said branches including a resistor providing a predetermined fixed resistance and a controllable resistance element connected in series; and a plurality of control amplifier means responsive to a common master control voltage and having respective outputs coupled to respective ones of said controllable resistance elements for providing a variable control voltage for the associated controllable resistance element over a preselected range of said master control voltage and for providing a first essentially constant control voltage for said controllable resistance element in response to a master control voltage below said preselected range and a second essentially constant control voltage for said controllable resistance element in response to a master control voltage above said preselected range, said first essentially constant control voltage being of a value to render said associated controllable resistance element heavily conductive of current, said second essentially constant control voltage being of a value to render said associated controllable resistance element essentially nonconductive of current, and said variable control voltage being in a range to render said associated controllable resistance element conductive of current at an intermediate level determined by the value of said master control voltage.

Claim 5

An electronically controlled variable impedance device comprising: a plurality of electrical circuit branches connected in parallel, at least certain ones of said branches each including a controllable impedance element and an element providing a preselected fixed impedance connected in series; and a plurality of control amplifiers, each responsive to a common master control voltage and a different reference voltage and having a different preselected gain with the output of each control amplifier being coupled to a different one of said controllable impedance elements, for providing a linearly variable control voltage for the associated controllable impedance element over a preselected range of said master control voltage centered essentially at said reference voltage and for providing a first essentially constant control voltage for said controllable impedance element when said master control voltage is below said preselected range and a second essentially constant control voltage for said controllable impedance element when said master control voltage is above said preselected range, said first essentially constant control voltage being of a value to render said associated controllable impedance element heavily conductive of current, said second essentially constant control voltage being of a value to render said associated controllable impedance element essentially nonconductive of current, and said linearly variable control voLtage being in a range to render said associated controllable impedance element conductive of current at an intermediate level determined by the value of said master control voltage.

Claim 6

An electronically controlled variable impedance device comprising: a plurality of electrical circuit branches connected in parallel, at least certain ones of said branches each including a controllable impedance element and an element providing a preselected fixed impedance connected in series; and a plurality of control amplifiers, each responsive to a common master control voltage and a different reference voltage and having a different preselected gain with the output of each control amplifier being coupled to a different one of said controllable impedance elements, for providing a linearly variable control voltage for the associated controllable impedance element over a preselected range of said master control voltage centered essentially at said reference voltage and for providing a first essentially constant control voltage for said controllable impedance element when said master control voltage is below said preselected range and a second essentially constant control voltage for said controllable impedance element when said master control voltage is above said preselected range, said first essentially constant control voltage being of a value to render said associated controllable impedance element heavily conductive of current, said second essentially constant control voltage being of a value to render said associated controllable impedance element essentially nonconductive of current, and said linearly variable control voLtage being in a range to render said associated controllable impedance element conductive of current at an intermediate level determined by the value of said master control voltage.

Claim 7

An electronically controlled variable impedance device comprising: a plurality of electrical circuit branches connected in parallel, at least certain ones of said branches each including a field effect transistor having its source-drain path connected in series with an element providing a preselected fixed impedance; a plurality of control amplifier means responsive to a common master control voltage and having respective outputs coupled to respective gate electrodes of said field effect transistors for providing a variable field effect transistor control voltage for the associated field effect transistor over a preselected range of said master control voltage and for providing a first essentially constant field effect transistor control voltage in response to a master control voltage below said preselected range and a second essentially constant field effect transistor control voltage in response to a master control voltage above said preselected range, said first essentially constant field effect transistor control voltage being of a value to render said associated field effect transistor heavily conductive of current, said second essentially constant field effect transistor control voltage being of a value to render said associated field effect transistor essentially nonconductive of current, and said variable field effect transistor control voltage being in a range to render said associated field effect transistor conductive of current at an intermediate level determined by the value of said master control voltage.

Claim 8

An electronically controlled variable impedance device comprising: a plurality of electrical circuit branches connected in parallel, at least certain ones of said branches each including a field effect transistor having its source-drain path connected in series with an element providing a preselected fixed impedance; a plurality of control amplifier means responsive to a common master control voltage and having respective outputs coupled to respective gate electrodes of said field effect transistors for providing a variable field effect transistor control voltage for the associated field effect transistor over a preselected range of said master control voltage and for providing a first essentially constant field effect transistor control voltage in response to a master control voltage below said preselected range and a second essentially constant field effect transistor control voltage in response to a master control voltage above said preselected range, said first essentially constant field effect transistor control voltage being of a value to render said associated field effect transistor heavily conductive of current, said second essentially constant field effect transistor control voltage being of a value to render said associated field effect transistor essentially nonconductive of current, and said variable field effect transistor control voltage being in a range to render said associated field effect transistor conductive of current at an intermediate level determined by the value of said master control voltage.

Claim 9

An electronically controlled variable impedance device according to claim 1 wherein each of said control amplifier means includes an operational amplifier, a voltage divider, means for applying said master control voltage to one terminal of said voltage divider, means for applying a reference voltage to another terminal of said voltage divider, and said voltage divider having an intermediate terminal coupled to a noninverting input terminal of said operational amplifier.

Claim 10

An electronically controlled variable impedance device according to claim 5 wherein said voltage divider includes a first voltage divider resistor connected between said one and said intermediate terminals, and a second voltage divider resistor connected between said another and said intermediate terminals, said first and second voltage divider resistors providing the same resistance.

Claim 11

An electronically controlled variable impedance device according to claim 5 wherein each of said control amplifier means further includes first and second zener diodes coupled in series in opposite polarity between an inverting input terminal and an output terminal of said operational amplifier, and a third zener diode coupled between said operational amplifier output terminal and an output terminal of said control amplifier means.

Claim 12

An electronically controlled variable impedance device according to claim 3 wherein each of said control amplifier means includes an operational amplifier having a noninverting input terminal, an inverting input terminal, and an output terminal; first and second resistors each having one terminal connected to said inverting input terminal; means for applying said master control voltage to another terminal of said first resistor; means for applying said reference voltage to another terminal of said second resistor; a third resistor connected between said inverting input terminal and said output terminal of said operational amplifier; fourth and fifth resistors connected in series, a terminal of said fifth resistor electrically remote from said fourth resistor being connected to said inverting input terminal; first and second zener diodes connected in series in opposite polarity between said output terminal of said operational amplifier and the junction between said fourtH and fifth resistors; a third zener diode connected between said output terminal of said operational amplifier and an output terminal of said control amplifier means; a sixth resistor having one terminal connected to said output terminal of said control amplifier; and means for applying an operating potential between a terminal of said fourth resistor electrically remote from said fifth resistor and another terminal of said sixth resistor.