Video signal play-back circuit

Claim 2

A video signal play-back circuit comprising: a magnetic head which detects a video signal recorded on a magnetic recording medium; a resonance circuit which is electrically connected to said magnetic head so that the signal picked up by said magnetic head may be applied to said resonance circuit, and which includes an inductance element and a capacitance element including a variable capacitor for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the signal play-back circuit; an amplifier circuit having a field-effect transistor of which the gate terminal is connected with said resonance circuit to provide a high input impedance to said amplifier circuit; and .Iadd.means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising .Iaddend. a variable resistor which is connected between one output terminal of said amplifier circuit and one terminal of said resonance circuit and which .[.serves to adjust a quality factor Q of said resonance circuit.]. .Iadd.has a value of resistance which sets the quality factor Q of said resonance circuit at a value between 2 and 4.Iaddend..

Claim 3

A signal play-back circuit according to claim 1, wherein a capacitor for cutting off direct current is connected in series with the Q adjusting resistor.

Claim 4

A signal play-back circuit according to claim 1, wherein an inductance which said magnetic head has is included as said inductance element of said resonance circuit.

Claim 5

A signal play-back circuit according to claim 1, wherein the Q adjusting resistor has a resistance value R 1 which is greater than a resistance value R 0 in the case where it is connected across said one terminal of said resonance circuit and a reference terminal in order to attain the same resonance characteristic.

Claim 6

A signal play-back signal according to claim 1 or 7, wherein the Q adjusting resistor has a resistance value R 1 which is greater than an apparent resistance value R 0 between said one terminal of said resonance circuit and a reference terminal when said Q adjusting resistor is coupled in the circuit in order to attain the same resonance characteristic as if a physical resistor R 0 were coupled between said one terminal of the resonance circuit and said reference terminal.

Claim 7

A signal play-back circuit according to claim 5, wherein said reference terminal is coupled to ground.

Claim 8

A video signal play-back circuit comprising: a rotating magnetic head which detects a video signal recorded on a magnetic recording medium; a rotary transformer which derives a signal from the rotating magnetic head; a boosting transformer which boosts a signal from said rotary transformer; a resonance circuit which is electrically connected to said boosting transformer in order to improve a frequency characteristic of an output signal of said boosting transformer and which includes an inductance element and a capacitance element including a variable capacitor for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the signal play-back circuit; an amplifier circuit having a field-effect transistor of which the gate terminal is connected with said resonance circuit to provide a high input impedance to said amplifier circuit; and .Iadd.means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising .Iaddend. a variable resistor which is connected between one output terminal of said amplifier circuit and one terminal of said resonance circuit and which .[.serves to adjust a quality factor Q of said resonance circuit.]. .Iadd.has a value of resistance which sets the quality factor Q of said resonance circuit at a value between 2 and 4.Iaddend..

Claim 9

A video signal play-back circuit comprising: a rotating magnetic head which detects a video signal recorded on a magnetic recording medium; a rotary transformer which derives a signal from the rotating magnetic head; a boosting transformer which boosts a signal from said rotary transformer; a resonance circuit which is electrically connected to said boosting transformer in order to improve a frequency characteristic of an output signal of said boosting transformer and which includes an inductance element and a capacitance element including a variable capacitor for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the signal play-back circuit; an amplifier circuit having a field-effect transistor of which the gate terminal is connected with said resonance circuit to provide a high input impedance to said amplifier circuit; and .Iadd.means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising .Iaddend. a variable resistor which is connected between one output terminal of said amplifier circuit and one terminal of said resonance circuit and which .[.serves to adjust a quality factor Q of said resonance circuit.]. .Iadd.has a value of resistance which sets the quality factor Q of said resonance circuit at a value between 2 and 4.Iaddend..

Claim 10

A video signal play-back circuit comprising: a rotating magnetic head which detects a video signal recorded on a magnetic recording medium; a rotary transformer which derives a signal from the rotating magnetic head; a boosting transformer coupled to a secondary coil of said rotary transformer to boost a signal from said rotary transformer; a resonance circuit which is electrically connected to said boosting transformer in order to improve a frequency characteristic of an output signal of said boosting transformer, and which includes an inductance element and a capacitance element including a variable capacitor coupled across a secondary coil of said boosting transformer for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the signal play-back circuit; an amplifier circuit having a field-effect transistor of which the gate terminal is connected with said resonance circuit to provide a high input impedance to said amplifier circuit; and .Iadd.means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising.Iaddend. a variable resistor which is connected between one output terminal of said amplifier circuit and one terminal of said resonance circuit and which .[.serves to adjust a quality factor Q of said resonance circuit.]. .Iadd.has a value of resistance which sets the quality factor Q of said resonance circuit at a value between 2 and 4, .Iaddend.wherein the Q adjusting resistor has a resistance value R 1 which is greater than an apparent resistance value R 0 across the variable capacitor of said resonance circuit when said Q adjusting resistor is coupled in the circuit in order to attain the same resonance characteristic as if a physical resistor R 0 were coupled across the variable capacitor. .Iadd.

Claim 11

A video signal play-back circuit comprising: a rotating magnetic head which detects a video signal recorded on a magnetic recording medium; a rotary transformer which derives a signal from the rotating magnetic head; a boosting transformer coupled to a secondary coil of said rotary transformer to boost a signal from said rotary transformer; a resonance circuit which is electrically connected to said boosting transformer in order to improve a frequency characteristic of an output signal of said boosting transformer, and which includes an inductance element and a capacitance element including a variable capacitor coupled across a secondary coil of said boosting transformer for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the signal play-back circuit; an amplifier circuit having a field-effect transistor of which the gate terminal is connected with said resonance circuit to provide a high input impedance to said amplifier circuit; and .Iadd.means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising.Iaddend. a variable resistor which is connected between one output terminal of said amplifier circuit and one terminal of said resonance circuit and which .[.serves to adjust a quality factor Q of said resonance circuit.]. .Iadd.has a value of resistance which sets the quality factor Q of said resonance circuit at a value between 2 and 4, .Iaddend.wherein the Q adjusting resistor has a resistance value R 1 which is greater than an apparent resistance value R 0 across the variable capacitor of said resonance circuit when said Q adjusting resistor is coupled in the circuit in order to attain the same resonance characteristic as if a physical resistor R 0 were coupled across the variable capacitor. .Iadd.

Claim 12

A video signal play-back circuit comprising: a magnetic head which detects a video signal recorded on a magnetic recording medium and produces an output signal representative of said video signal; a resonance circuit which is electrically connected to receive the output signal of said magnetic head, and which includes an inductance element and a capacitance element including a variable capacitor for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the signal play-back circuit by compensating the frequency characteristic of the output signal of the magnetic head; an amplifier circuit which amplifies a signal from said resonance circuit; and means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising a variable resistor which is connected as a negative feedback resistor between one output terminal of said amplifier circuit and one terminal of said resonance circuit as a resistor for said resonance circuit which has a value of resistance which sets the quality factor Q of said resonance circuit at a value between 2 and 4. .Iaddend. .Iadd.10. A video signal play-back circuit comprising: a rotating magnetic head which detects a video signal recorded on a magnetic recording medium and produces an output signal representative of said video signal; a rotary transformer which derives a signal from the output signal of the rotating magnetic head; a boosting transformer which boosts a signal from said rotary transformer; a resonance circuit which is electrically connected to said boosting transformer in order to improve a frequency characteristic of an output signal of said boosting transformer to thereby compensate the frequency characteristics of the output signal of the magnetic head, wherein said resonance circuit includes an inductance element and a capacitance element including a variable capacitor for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the signal play-back circuit by the compensation of the magnetic head output signal frequency characteristic; an amplifier circuit which amplifies a signal from said resonance circuit; and means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising a variable resistor which is connected as a negative feedback resistor between one output terminal of said amplifier circuit and one terminal of said resonance circuit as a resistor for the resonance circuit which has a value of resistance which sets the quality factor Q of said resonance

Claim 13

A video signal play-back circuit comprising: a magnetic head which detects a video signal recorded on a magnetic recording medium and produces an output signal representative of said video signal; a resonance circuit which is electrically connected to receive the output signal of said magnetic head, and which includes an inductance element and a capacitance element including a variable capacitor for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the signal play-back circuit by compensating the frequency characteristic of the output signal of the magnetic head; an amplifier circuit which amplifies a signal from said resonance circuit; and means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising a variable resistor which is connected as a negative feedback resistor between one output terminal of said amplifier circuit and one terminal of said resonance circuit as a resistor for said resonance circuit which has a value of resistance which sets the quality factor Q of said resonance circuit at a value between 2 and 4. .Iaddend. .Iadd.10. A video signal play-back circuit comprising: a rotating magnetic head which detects a video signal recorded on a magnetic recording medium and produces an output signal representative of said video signal; a rotary transformer which derives a signal from the output signal of the rotating magnetic head; a boosting transformer which boosts a signal from said rotary transformer; a resonance circuit which is electrically connected to said boosting transformer in order to improve a frequency characteristic of an output signal of said boosting transformer to thereby compensate the frequency characteristics of the output signal of the magnetic head, wherein said resonance circuit includes an inductance element and a capacitance element including a variable capacitor for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the signal play-back circuit by the compensation of the magnetic head output signal frequency characteristic; an amplifier circuit which amplifies a signal from said resonance circuit; and means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising a variable resistor which is connected as a negative feedback resistor between one output terminal of said amplifier circuit and one terminal of said resonance circuit as a resistor for the resonance circuit which has a value of resistance which sets the quality factor Q of said resonance

Claim 14

circuit at a value between 2 and 4. .Iaddend. .Iadd.11. A video signal play-back circuit comprising: a rotating magnetic head which detects a video signal recorded on a magnetic recording medium and produces an output signal representative of said video signal; a rotary transformer which derives a signal from the rotating magnetic head; a boosting transformer coupled to a secondary coil of said rotary transformer to boost a signal from said rotary transformer; a resonance circuit which is electrically connected to said boosting transformer in order to improve a frequency characteristic of an output signal of said boosting transformer to thereby compensate the frequency characteristics of the output signal of the magnetic head, wherein said resonance circuit includes an inductance element and a capacitance element including a variable capacitor coupled across a secondary coil of said boosting transformer for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the signal play-back circuit by the compensation of the magnetic head output signal frequency characteristic; an amplifier circuit which amplifies a signal from said resonance circuit; and means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising a variable resistor which is connected as a negative feedback resistor between one output terminal of said amplifier circuit and one terminal of said resonance circuit as a resistor for the resonance circuit which has a value of resistance which sets the quality factor Q of said resonance circuit at a value between 2 and 4, wherein the Q adjusting resistor has a resistance value R 1 which is greater than an apparent resistance value R 0 across the variable capacitor of said resonance circuit when said Q adjusting resistor is coupled in the circuit in order to attain the same resonance characteristic as if a physical resistor R 0 were

Claim 15

circuit at a value between 2 and 4. .Iaddend. .Iadd.11. A video signal play-back circuit comprising: a rotating magnetic head which detects a video signal recorded on a magnetic recording medium and produces an output signal representative of said video signal; a rotary transformer which derives a signal from the rotating magnetic head; a boosting transformer coupled to a secondary coil of said rotary transformer to boost a signal from said rotary transformer; a resonance circuit which is electrically connected to said boosting transformer in order to improve a frequency characteristic of an output signal of said boosting transformer to thereby compensate the frequency characteristics of the output signal of the magnetic head, wherein said resonance circuit includes an inductance element and a capacitance element including a variable capacitor coupled across a secondary coil of said boosting transformer for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the signal play-back circuit by the compensation of the magnetic head output signal frequency characteristic; an amplifier circuit which amplifies a signal from said resonance circuit; and means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising a variable resistor which is connected as a negative feedback resistor between one output terminal of said amplifier circuit and one terminal of said resonance circuit as a resistor for the resonance circuit which has a value of resistance which sets the quality factor Q of said resonance circuit at a value between 2 and 4, wherein the Q adjusting resistor has a resistance value R 1 which is greater than an apparent resistance value R 0 across the variable capacitor of said resonance circuit when said Q adjusting resistor is coupled in the circuit in order to attain the same resonance characteristic as if a physical resistor R 0 were

Claim 16

coupled across the variable capacitor. .Iaddend. .Iadd.12. A video signal play-back circuit comprising: a magnetic head which detects a frequency modulated video signal having a predetermined carrier frequency and recorded on a magnetic recording medium; a resonance circuit which is electrically connected to said magnetic head so that the signal picked up by said magnetic head may be applied to said resonance circuit, and which includes an inductance element and a capacitance element including a variable capacitor for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the output signal of said magnetic head, the resonance frequency of said resonance circuit being equal to or higher than said carrier frequency; an amplifier circuit amplifying an output signal of said resonance circuit; and means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising a variable resistor which is connected between one output terminal of said amplifier circuit and one terminal of said resonance circuit and which has a value of resistance which sets the quality factor Q of said resonance

Claim 17

coupled across the variable capacitor. .Iaddend. .Iadd.12. A video signal play-back circuit comprising: a magnetic head which detects a frequency modulated video signal having a predetermined carrier frequency and recorded on a magnetic recording medium; a resonance circuit which is electrically connected to said magnetic head so that the signal picked up by said magnetic head may be applied to said resonance circuit, and which includes an inductance element and a capacitance element including a variable capacitor for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the output signal of said magnetic head, the resonance frequency of said resonance circuit being equal to or higher than said carrier frequency; an amplifier circuit amplifying an output signal of said resonance circuit; and means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising a variable resistor which is connected between one output terminal of said amplifier circuit and one terminal of said resonance circuit and which has a value of resistance which sets the quality factor Q of said resonance

Claim 18

circuit at a value between 2 and 4. .Iaddend. .Iadd.13. A video signal play-back circuit comprising: a rotating magnetic head which detects a frequency modulated video signal having a predetermined carrier frequency and recorded on a magnetic recording medium; a rotary transformer which derives a signal from the rotating magnetic head; a boosting transformer which boosts a signal from said rotary transformer; a resonance circuit which is electrically connected to said boosting transformer in order to improve a frequency characteristic of an output signal of said boosting transformer and which includes an inductance element and a capacitance element including a variable capacitor for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the output signal of said boosting transformer, the resonance frequency of said resonance circuit being equal to or higher than said carrier frequency; an amplifier circuit amplifying an output signal of said resonance circuit; and means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising a variable resistor which is connected between one output terminal of said amplifier circuit and one terminal of said resonance circuit and which has a value of resistance which sets the quality factor Q of said resonance circuit at a value between 2 and 4. .Iaddend. .Iadd.14. A video signal play-back circuit comprising: a rotating magnetic head which detects a frequency modulated video signal having a predetermined carrier frequency and recorded on a magnetic recording medium; a rotary transformer which derives a signal from the rotating magnetic head; a boosting transformer coupled to a secondary coil of said rotary transformer to boost a signal from said rotary transformer; a resonance circuit which is electrically connected to said boosting transformer in order to improve a frequency characteristic of an output signal of said boosting transformer, and which includes an inductance element and a capacitance element including a variable capacitor coupled across a secondary coil of said boosting transformer for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the output signal of said boosting transformer, the resonance frequency of said resonance circuit being equal to or higher than said carrier frequency; an amplifier circuit amplifying an output signal of said resonance circuit; and means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising a variable resistor which is connected between one output terminal of said amplifier circuit and one terminal of said resonance circuit and which has a value of resistance which sets the quality factor Q of said resonance circuit at a value between 2 and 4, wherein the Q adjusting resistor has a resistance value R 1 which is greater than an apparent resistance value R 0 across the variable capacitor of said resonance circuit when said Q adjusting resistor is coupled in the circuit in order to attain the same resonance characteristic as if a physical resistor R 0 were coupled across the variable capacitor..Iaddend.

Claim 19

circuit at a value between 2 and 4. .Iaddend. .Iadd.13. A video signal play-back circuit comprising: a rotating magnetic head which detects a frequency modulated video signal having a predetermined carrier frequency and recorded on a magnetic recording medium; a rotary transformer which derives a signal from the rotating magnetic head; a boosting transformer which boosts a signal from said rotary transformer; a resonance circuit which is electrically connected to said boosting transformer in order to improve a frequency characteristic of an output signal of said boosting transformer and which includes an inductance element and a capacitance element including a variable capacitor for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the output signal of said boosting transformer, the resonance frequency of said resonance circuit being equal to or higher than said carrier frequency; an amplifier circuit amplifying an output signal of said resonance circuit; and means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising a variable resistor which is connected between one output terminal of said amplifier circuit and one terminal of said resonance circuit and which has a value of resistance which sets the quality factor Q of said resonance circuit at a value between 2 and 4. .Iaddend. .Iadd.14. A video signal play-back circuit comprising: a rotating magnetic head which detects a frequency modulated video signal having a predetermined carrier frequency and recorded on a magnetic recording medium; a rotary transformer which derives a signal from the rotating magnetic head; a boosting transformer coupled to a secondary coil of said rotary transformer to boost a signal from said rotary transformer; a resonance circuit which is electrically connected to said boosting transformer in order to improve a frequency characteristic of an output signal of said boosting transformer, and which includes an inductance element and a capacitance element including a variable capacitor coupled across a secondary coil of said boosting transformer for adjusting the resonance frequency of the resonance circuit for equalization of the frequency characteristic of the output signal of said boosting transformer, the resonance frequency of said resonance circuit being equal to or higher than said carrier frequency; an amplifier circuit amplifying an output signal of said resonance circuit; and means for adjusting a quality factor Q of said resonance circuit without any substantial increase in thermal noise of said resonance circuit, said means comprising a variable resistor which is connected between one output terminal of said amplifier circuit and one terminal of said resonance circuit and which has a value of resistance which sets the quality factor Q of said resonance circuit at a value between 2 and 4, wherein the Q adjusting resistor has a resistance value R 1 which is greater than an apparent resistance value R 0 across the variable capacitor of said resonance circuit when said Q adjusting resistor is coupled in the circuit in order to attain the same resonance characteristic as if a physical resistor R 0 were coupled across the variable capacitor..Iaddend.