Direct coupled amplifier in null balance circuit or the like

Claim 2

A circuit for achievement of null balance comprising in combination with a signal input terminal and a reference terminal: switch means with an output terminal intermittently shifted between connection to the signal input terminal and the reference terminal, a voltage divider connected between the signal input terminal and the reference terminal, an average voltage terminal connected to an intermediate point on the voltage divider, a differential amplifier with first and second input terminals and an output terminal, the first being directly connected to the switch means output terminal and the second being connected to the average voltage terminal, an adjustable-voltage source of reference voltage with adjusting means, said source being connected to said reference terminal, and driving means responsive to output of said differential amplifier for driving said adjusting means.

Claim 3

A circuit as defined in claim 1 wherein the differential amplifier has a polarized output and the driving means is reversible in response to reverse polarity of the output of the differential amplifier.

Claim 4

A moving pen chart recorder employing the null balance circuit defined in claim 1 wherein the recorder has a moving pen operatively connected to said driving means.

Claim 5

The chart recorder defined in claim 3 wherein the moving pen has a limit stop and said driving means includes a slip clutch interposed in the connection to said moving pen, and an input limiter is connected to said input terminal.

Claim 6

The circuit as defined in claim 1 wherein the voltage divider comprises a pair of series-connected, equal resistances with the voltage terminal situated at the junction thereof, whereby the voltage level established at said voltage terminal and supplied to the second input terminal of the differential amplifier is the average of the voltages at the signal input terminal and the reference terminal.

Claim 7

A moving pen chart recorder comprising in combination with a signal input terminal and a reference terminal: a chopper with an output terminal intermittently shifted between connection to the signal input terminal and the reference terminal, an average voltage terminal and means for supplying thereto a potential intermediate that between the signal input terminal and the reference terminal, a differential amplifier with first and second input terminals and an output terminal, the first being directly connected to the chopper outPut terminal and the second being connected to the average voltage terminal, an adjustable-voltage source of reference voltage with adjusting means, said source being connected to said reference voltage terminal, driving means responsive to output of said differential amplifier for driving said adjusting means to achieve a null balance, a moving pen operatively connected to said driving means, said moving pen having a limit stop and said driving means including a slip clutch interposed in the connection to said moving pen, an impedance having an intermediate terminal, said impedance being connected in series between the signal input terminal and the chopper, and an input limiter connected in shunt to said intermediate terminal.

Claim 8

A moving pen chart recorder comprising in combination with a signal input terminal and a reference terminal: a chopper with an output terminal intermittently shifted between connection to the signal input terminal and the reference terminal, an average voltage terminal and means for supplying thereto a potential intermediate that between the signal input terminal and the reference terminal, a differential amplifier with first and second input terminals and an output terminal, the first being directly connected to the chopper outPut terminal and the second being connected to the average voltage terminal, an adjustable-voltage source of reference voltage with adjusting means, said source being connected to said reference voltage terminal, driving means responsive to output of said differential amplifier for driving said adjusting means to achieve a null balance, a moving pen operatively connected to said driving means, said moving pen having a limit stop and said driving means including a slip clutch interposed in the connection to said moving pen, an impedance having an intermediate terminal, said impedance being connected in series between the signal input terminal and the chopper, and an input limiter connected in shunt to said intermediate terminal.

Claim 9

The chart recorder defined in claim 6 wherein the input limiter comprises means for supplying positive and negative voltages corresponding to the chart pen positions for the limit stops, a pair of differential amplifiers each having an output terminal, a first input terminal connected to said intermediate terminal and a second input terminal, one of the second input terminals being connected to the positive voltage supply means and the other being connected to the negative voltage supply means, and a pair of rectifiers connected in series between said differential amplifier output terminals with a common terminal connected to said intermediate terminal.

Claim 10

The chart recorder defined in claim 7 wherein the chopper comprises a pair of field effect transistors, each having a drain, a gate and a source, and a triggered switching circuit with opposite polarity output terminals each connected to the first input terminal of the differential amplifier, one drain being operatively connected to the signal input terminal and the other drain being operatively connected to the reference terminal.

Claim 11

A circuit for achievement of null balance comprising in combination with a signal input terminal and a reference terminal: a pair of field-effect transistors, each having a drain, a gate and a source, a triggered switching circuit with opposite polarity output terminals each connected to a different one of said gates, an average voltage terminal and means for supplying thereto a potential intermediate that between the signal input terminal and the reference terminal, a differential amplifier with first and second input terminals and an output terminal, adjustable voltage source of reference voltage with adjusting means, said source being connected to said reference terminal, driving means responsive to the output of said differential amplifier for driving said adjusting means, and the field effect transistor sources being directly connected to the first input terminal of the differential amplifier, one drain being operatively connected to the signal input terminal and the other drain being operatively connected to the reference terminal, the second differential amplifier input terminal being connected to the average voltage terminal.

Claim 12

A circuit for achievement of null balance comprising in combination with a signal input terminal and a reference terminal: a pair of field-effect transistors, each having a drain, a gate and a source, a triggered switching circuit with opposite polarity output terminals each connected to a different one of said gates, an average voltage terminal and means for supplying thereto a potential intermediate that between the signal input terminal and the reference terminal, a differential amplifier with first and second input terminals and an output terminal, adjustable voltage source of reference voltage with adjusting means, said source being connected to said reference terminal, driving means responsive to the output of said differential amplifier for driving said adjusting means, and the field effect transistor sources being directly connected to the first input terminal of the differential amplifier, one drain being operatively connected to the signal input terminal and the other drain being operatively connected to the reference terminal, the second differential amplifier input terminal being connected to the average voltage terminal.

Claim 13

In a null balance circuit employing a signal input terminal receiving a signal input voltage, a reference terminal receiving a reference voltage from a motor driven follow-up potentiometer, a chopper which switches between the signal input and reference terminals to produce a chopper output signal, the improvement which comprises: a differential amplifier with a first input terminal directly connected to the chopper to receive the chopper output signal, a second input terminal, and an output terminal to which the motor is operatively connected, and means for supplying the average of the signal input voltage and the reference voltage to the second input terminal of the differential amplifier whereby the differential amplifier compares the chopper output signal supplied to the first input terminal with the average value of the signal input voltage and the reference voltage, and the motor adjusts the value of the reference voltage until the output of the Differential amplifier falls to zero and the motor stops.

Claim 14

In a null balance circuit employing a signal input terminal receiving a signal input voltage, a reference terminal receiving a reference voltage from a motor driven follow-up potentiometer, a chopper which switches between the signal input and reference terminals to produce a chopper output signal, the improvement which comprises: a differential amplifier with a first input terminal directly connected to the chopper to receive the chopper output signal, a second input terminal, and an output terminal to which the motor is operatively connected, and means for supplying the average of the signal input voltage and the reference voltage to the second input terminal of the differential amplifier whereby the differential amplifier compares the chopper output signal supplied to the first input terminal with the average value of the signal input voltage and the reference voltage, and the motor adjusts the value of the reference voltage until the output of the Differential amplifier falls to zero and the motor stops.

Claim 15

A circuit comprising the combination of: a signal input terminal for receiving a signal input voltage; a reference terminal for receiving a reference voltage; switch means with an output terminal alternately connected to the signal input terminal and the reference terminal; a differential amplifier with first and second input terminals and an output terminal; means for directly connecting the output terminal of said switch means to the first input terminal of said differential amplifier; a voltage terminal; means for deriving a potential at the voltage terminal which is intermediate and a function of the signal input voltage and the reference voltage; and means for connecting the voltage terminal to the second input terminal of said differential amplifier.

Claim 16

A circuit comprising the combination of: a signal input terminal for receiving a signal input voltage; a reference terminal for receiving a reference voltage; switch means with an output terminal alternately connected to the signal input terminal and the reference terminal; a differential amplifier with first and second input terminals and an output terminal; means for directly connecting the output terminal of said switch means to the first input terminal of said differential amplifier; a voltage terminal; means for deriving a potential at the voltage terminal which is intermediate and a function of the signal input voltage and the reference voltage; and means for connecting the voltage terminal to the second input terminal of said differential amplifier.

Claim 17

The circuit of claim 11 wherein said means for deriving includes a voltage divider connected to the signal input terminal and the reference terminal for deriving said potential as the average value of the signal input voltage and the reference voltage.

Claim 18

The circuit of claim 11 wherein said means for deriving includes first and second equal resistances connected in series between the signal input terminal and the reference terminal, said voltage terminal being situated at the common point between said first and second resistances.

Claim 19

The circuit of claim 11 further including means connected between the output terminal of said differential amplifier and the reference terminal for adjusting the value of said reference voltage to achieve null balance of the circuit.