Differential amplifier circuit for servo system

Claim 2

An electric circuit for a servo system, comprising: a first differential circuit to produce a direct-current signal corresponding to a deviation of an input signal from a reference value to be set, said differential circuit having two output terminals; two semiconductor switching circuits connected to said output terminals of said differential circuit, respectively, each of said switching circuits including a second differential circuit having a first transistor, the input terminal of which is electrically connected to one of the two output terminals of said first differential circuit, and a second transistor, the input terminal of which is electrically connected to a constant voltage for applying a reference voltage to said second differential circuit and bias level varying means for varying the reference voltage; an astable multivibrator having at least one output terminal and iNput terminals electrically connected to the output terminals of said second differential circuits, said astable multivibrator being constituted so as to produce an alternating pulse current having a variable and reversible direct-current component in response to the output of said second differential circuits and to produce such pulse current only when at least one of said second differential circuits provides an output to an input of said astable multivibrator; servo control means electrically connected to the output of said astable multivibrator, said servo control means including means for causing the input to said first differential circuit to approximate said reference voltage, whereby upper and lower limits of a non-sensitive range of said servo control means are controllable by said bias level varying means which varies the reference voltage level and in turn operating points of said second differential circuits.

Claim 3

A servo system of the balance restoring type comprising: an input transducer adapted to produce an input electrical signal; a signal modification means adapted to act directly or indirectly on said electrical input signal produced by said input transducer to increase or decrease the electrical signal produced by it; an astable multivibrator having two output terminals at which pulse currents of opposite polarity are respectively produced in alternation during operation of said multivibrator, the pulse lengths of the pulse currents being variable by controlling said input transducer so that when the pulse length at one of said terminals is varied, the pulse length at the other terminal is maintained at constant value; output transducer means electrically connected between said two output terminals of said astable multivibrator, said output transducer including means to modify said input signal so that it is brought approximately equal to a reference value thereof, at the input of said signal modification means; a first differential circuit for producing a direct-current signal corresponding to a deviation of said input signal from the reference value, said differential circuit having a first and a second output terminal; two semiconductor switching circuits connected to said two output terminals of said first differential circuit, respectively, each of said of said switching circuits including, a second differential circuit having a first transistor, the input terminal of which is electrically connected to one of the two output terminals of said first differential circuit, and a second transistor, the input terminal of which is electrically connected to a constant voltage circuit for applying a reference voltage to said second differential circuit and bias level varying means for varying the reference voltage, and an auxiliary switching circuit subject to on-off control in response to the output of said second differential circuit, said auxiliary switching circuit having an input terminal electrically connected to the output terminals of said second differential circuit and an output terminal electrically connected to one of the input terminals of said astable multivibrator, said astable multivibrator being constituted so that it does not operate to produce pulses unless at least one of said auxiliary switching circuits is switched on; whereby the non-sensitive range of said multivibrator is adjustable by said bias level varying means, which modulate the output of said input transducer to vary the operating points of said auxiliary switching circuits.

Claim 4

A servo system of the balance restoring type comprising: an input transducer adapted to produce an input electrical signal; a signal modification means adapted to act directly or indirectly on said electrical input signal produced by said input transducer to increase or decrease the electrical signal produced by it; an astable multivibrator having two output terminals at which pulse currents of opposite polarity are respectively produced in alternation during operation of said multivibrator, the pulse lengths of the pulse currents being variable by controlling said input transducer so that when the pulse length at one of said terminals is varied, the pulse length at the other terminal is maintained at constant value; output transducer means electrically connected between said two output terminals of said astable multivibrator, said output transducer including means to modify said input signal so that it is brought approximately equal to a reference value thereof, at the input of said signal modification means; a first differential circuit for producing a direct-current signal corresponding to a deviation of said input signal from the reference value, said differential circuit having a first and a second output terminal; two semiconductor switching circuits connected to said two output terminals of said first differential circuit, respectively, each of said of said switching circuits including, a second differential circuit having a first transistor, the input terminal of which is electrically connected to one of the two output terminals of said first differential circuit, and a second transistor, the input terminal of which is electrically connected to a constant voltage circuit for applying a reference voltage to said second differential circuit and bias level varying means for varying the reference voltage, and an auxiliary switching circuit subject to on-off control in response to the output of said second differential circuit, said auxiliary switching circuit having an input terminal electrically connected to the output terminals of said second differential circuit and an output terminal electrically connected to one of the input terminals of said astable multivibrator, said astable multivibrator being constituted so that it does not operate to produce pulses unless at least one of said auxiliary switching circuits is switched on; whereby the non-sensitive range of said multivibrator is adjustable by said bias level varying means, which modulate the output of said input transducer to vary the operating points of said auxiliary switching circuits.

Claim 5

An electric circuit according to claim 1, wherein said bias level varying means is provided with a variable resistor connected to said constant voltage circuit, said variable resistor varying the output current of said constant voltage circuit at a predetermined constant voltage.

Claim 6

An electric circuit according to claim 1, wherein said differential circuits and said semiconductor switching circuit are each of electrically symmetrical configurAtion.

Claim 7

An electric circuit according to claim 1, wherein said driving means is provided with warning means electrically connected to said semiconductor switching means.

Claim 8

An electric circuit according to claim 2, wherein said astable multivibrator includes a differential circuit having a couple of transistors, and a time constant circuit connected to the inputs of said couple of transistors and having a capacitor and resistors different in resistance.

Claim 9

An electric circuit according to claim 2, wherein said input transducer is provided with warning means electrically connected to said semiconductor switching means.

Claim 10

An electric circuit according to claim 1, wherein said semiconductor switching circuit is provided in the form of an integrated circuit.

Claim 11

A servo system according to claim 2, wherein said semiconductor switching circuit is provided in the form of an integrated circuit.

Claim 12

A servo system according to claim 2, wherein said bias level varying means is provided with a variable resistor connected in said constant voltage circuit, said variable resistor causing the output current of said constant voltage circuit to vary so as to produce a voltage of predetermined relation to the variable resistor setting.