Sample and hold circuit for an electronic organ

Claim 2

An electric organ, comprising an array of keys of said organ, a resistance having points corresponding respectively with said keys, means responsive to actuation of any selected key of said array of keys for providing a physically undgrounded point of zero voltage at a point of said resistance corresponding with the selected key, said resistance having an invariable point of reference potential, means including a feedback loop for maintaining the voltage of said invariable point of reference potential constant where any of said keys is actuated by feeding back current through said resistance in amplitude sufficient to maintain constant said voltage of said invariable point of reference potential, said feedback loop including a storage capacity, a voltage controlled tone signal oscillator responsive to the voltage of a point of said feedback loop, and means for acoustically transducing said tone signal.

Claim 3

The combination according to claim 1, wherein is included, a further high gain high input resistance feedback loop, means responsive to closure of any selected one of said key switches for controlling the voltage drops along said array of series connected resistances to provide said zero voltage at a junction of said array corresponding with the selected one of said key switches in response to the feedback action of said further feedback loop.

Claim 4

The combination according to claim 1, wherein is included a further high gain high input resistance feedback loop, means responsive to closure of any selected plurality of said key switches for controlling the voltage drops along said array of series connected resistances to provide said zero voltage point at a junction of said array corresponding with that one of said key switches corresponding with the highest note represented by said selected plurality of said key switches in response to the action of said further feedback loop.

Claim 5

The combination according to claim 1, wherein said means responsive to any selected key of said array of keys includes a voltage divider having points each corresponding with one of said first mentioned points, normally open electronic switches closable in response to actuations of said keys and each connecting one of said points of said resistance with one of said points of said voltage divider, and a further feedback loop between said voltage divider and said resistance.

Claim 6

An electric organ, comprising an array of key switches, a resistance, means responsive to operation of any combination of said key switches for adjusting the value of said resistance by providing one physically undergrounded point of zero voltage at any of plural preselected discrete points of said resistance corresponding with only one of said key switches, circuit means including a voltage comparator extending from an invariable point of said resistance to an output point, a resistive feedback loop extending from said output point to said further invariable point, a source of reference voltage, means for developing an input error signal for said voltage comparator as the difference of said reference voltage and the voltage of said invariable point, a voltage controlled tone signal source connected to said output point, and means for acoustically transducing the signal output of said tone signal source.

Claim 7

An electric organ, comprising an array of key switches, a resistance, means responsive to operation of any combination of said key switches for adjusting the value of said resistance by providing one physically undergrounded point of zero voltage at any of plural preselected discrete points of said resistance corresponding with only one of said key switches, circuit means including a voltage comparator extending from an invariable point of said resistance to an output point, a resistive feedback loop extending from said output point to said further invariable point, a source of reference voltage, means for developing an input error signal for said voltage comparator as the difference of said reference voltage and the voltage of said invariable point, a voltage controlled tone signal source connected to said output point, and means for acoustically transducing the signal output of said tone signal source.

Claim 8

The combination according to claim 5, wherein is provided a storage capacitor coupled to the output circuit of said amplifier to store the output voltage of said voltage comparator, and means responsive to said error signal for supplying charge to and abstracting charge from said storage capacitor as a function of the voltage of said invariable point.

Claim 9

The combination according to claim 5, wherein said resistance includes plural arrays of series connected resistances, said arrays being connected in series, said arrays having junctions corresponding one-for-one with said key switches, further feedback loops, each including one of said arrays and all including a common high gain high input resistance operational amplifier, means responsive to closure of any selected plurality of said key switches concurrently for completing only that one of said feedback loops corresponding with that one of said arrays containing a junction corresponding with the highest pitched one of said key switches, and means further responsive to said closure of said selected plurality of said key switches to provide said undergrounded point of zero voltage at the last mentioned junction in response to the action of said further feedback loop.

Claim 10

The combination according to claim 5, wherein said means responsive to operation of said key switches includes a separate normally open solid state switch operatively associated with each of said key switches, means responsive to closure of each of said key switches for rendering conductive the solid state switch associated with that key switch, a diode voltage divider chain interconnecting first corresponding terminals of said solid state switches to discrete points of said diode divider chain, said diode divider chain including identically poled diodes in series, a load circuit terminating said diode divider chain, a voltage comparator device including a source of reference potential and an input terminal for applying voltage for comparison with said reference potential by said voltage comparator device, and means responsive to the output of said comparison device for controlling the potential at said variable load circuit terminating said diode voltage divider chain, and means supplying voltage from one end of said resistance to said input terminal of said comparison device, said voltage comparison device providing a negative feedback lOop extending from said one end of said resistance to said variable load circuit, said voltage comparison device being arranged to draw substantially zero current from said resistance via said input terminal, and means connecting second terminals of said solid state switches to said discrete points of said resistance, said variable load circuit being a voltage responsive device responsive to control voltage to provide a variable load as a function of magnitude of said control voltage.

Claim 11

The combination according to claim 6, wherein said means responsive to actuation of any selected key of said array of keys includes a separate normally open solid state switch connected to be closed in response to operation of each of said keys, an amplifier, and a further feedback circuit extending through any closed ones of said solid state switches to the output of said amplifier and via said resistance to the input of said amplifier.

Claim 12

In an organ system, a chain of equal series connected resistances extending from a first point to a second point, a chain of equal impedances providing equal voltage drops thereacross extending from a third point to a fourth point, an amplifier having an input and an output, means applying a voltage to said first point, means connecting said second point to said input, means connecting any selected junctions of said resistances to selected ones of junctions of said impedances, means connecting said fourth point to said output, said third point floating, wherein is provided means for maintaining said first point at a fixed voltage, a voltage controlled tone signal oscillator, means responsive to said last means for controlling the frequency of said voltage controlled oscillator, and means for transducing the tone signal output of said oscillator.

Claim 13

In an organ system, a chain of equal series connected resistances extending from a first point to a second point, a chain of equal impedances providing equal voltage drops thereacross extending from a third point to a fourth point, an amplifier having an input and an output, means applying a voltage to said first point, means connecting said second point to said input, means connecting any selected junctions of said resistances to selected ones of junctions of said impedances, means connecting said fourth point to said output, said third point floating, wherein is provided means for maintaining said first point at a fixed voltage, a voltage controlled tone signal oscillator, means responsive to said last means for controlling the frequency of said voltage controlled oscillator, and means for transducing the tone signal output of said oscillator.

Claim 14

An electric organ, comprising an array of normally open key switches, an array of electronic switches, each of said key switches when closed rendering conductive one of said electronic switches, a series resistance chain having junctions corresponding one for one and each connected to one terminal of one of said electronic switches, a diode chain including series connected correspondingly poled diodes, means connecting the remaining terminals of said electronic switches one for one with corresponding electrodes of said diodes, a source of control voltage, means applying said control voltage to one end of said resistance chain, an amplifier having an input terminal and an output terminal, means connecting the other end of said resistance chain to said input terminal, means connecting one end of said diode chain to the output terminal of said amplifier, said resistance chain, diode chain and electronic switches being arranged and interconnected to provide a circuit from said source of control voltage through resistances of said resistance chain and via closed ones of said electronic switches and via said diode chain to said output terminal, and said resistance chain alone providing a circuit from said source of control voltage to said input terminal.

Claim 15

An electric organ, comprising an array of normally open key switches, an array of electronic switches, each of said key switches when closed rendering conductive one of said electronic switches, a series resistance chain having junctions corresponding one for one and each connected to one terminal of one of said electronic switches, a diode chain including series connected correspondingly poled diodes, means connecting the remaining terminals of said electronic switches one for one with corresponding electrodes of said diodes, a source of control voltage, means applying said control voltage to one end of said resistance chain, an amplifier having an input terminal and an output terminal, means connecting the other end of said resistance chain to said input terminal, means connecting one end of said diode chain to the output terminal of said amplifier, said resistance chain, diode chain and electronic switches being arranged and interconnected to provide a circuit from said source of control voltage through resistances of said resistance chain and via closed ones of said electronic switches and via said diode chain to said output terminal, and said resistance chain alone providing a circuit from said source of control voltage to said input terminal.

Claim 16

An electric organ, comprising a series connected array of resistances having a reference point, means including key switches for bringing any selected junction of said array of resistances to a physically ungrounded zero potential, said junction being a function of the operated key switches, a comparison circuit responsive to the voltage of said reference point and to a fixed reference voltage for generating an error signal, a storage capacitor, current source and drain means responsive to said error signal for controlling the charge of said capacitor, an output terminal, means amplifying the voltage across said storage capacitor to provide an amplified version of said voltage across said capacitor to said output terminal, a resistive feedback circuit extending from said output terminal to said reference point, a voltage controlled tone signal oscillator connected to said output terminal and responsive to the voltage of said output terminal to generAte tone frequency signals of variable frequency, and means for asoustically transducing said tone frequency signals.

Claim 17

An electric organ, comprising a series connected array of resistances having a reference point, means including key switches for bringing any selected junction of said array of resistances to a physically ungrounded zero potential, said junction being a function of the operated key switches, a comparison circuit responsive to the voltage of said reference point and to a fixed reference voltage for generating an error signal, a storage capacitor, current source and drain means responsive to said error signal for controlling the charge of said capacitor, an output terminal, means amplifying the voltage across said storage capacitor to provide an amplified version of said voltage across said capacitor to said output terminal, a resistive feedback circuit extending from said output terminal to said reference point, a voltage controlled tone signal oscillator connected to said output terminal and responsive to the voltage of said output terminal to generAte tone frequency signals of variable frequency, and means for asoustically transducing said tone frequency signals.

Claim 18

The combination according to claim 12, wherein is included means responsive to opening of all said key switches for disabling said current source and drain means for controlling said charge on said capacitor.

Claim 19

The combination according to claim 12, wherein said means including key switches for bringing any selected junction of said array of resistances to a physically ungrounded zero potential includes a voltage divider chain, solid sate switches responsive to closure of said key switches for connecting said selected junctions one for one with points of said voltage divider, and a further feedback circuit connecting an end point of said voltage divider with and end point of said array of resistances.

Claim 20

The combination according to claim 14, wherein said voltage divider is a series array of diodes each providing a fixed voltage drop.

Claim 21

The combination according to claim 15, wherein said switch means are solid state switch means.

Claim 22

The combination according to claim 16, wherein said impedances are diodes.

Claim 23

The combination according to claim 17, wherein said amplifier is a comparator, said voltage of said first point is positive, and the output of said comparator is negative.

Claim 24

The combination according to claim 18, wherein said chain of series connected resistances encompasses a resistance for each note of plural octaves of notes.