JP3550625B2 - Recording amplifier circuit - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a recording amplifier circuit for effectively improving the characteristics of a rotary transformer having a cutoff characteristic in a low frequency region in a magnetic recording device.
[0002]
[Prior art]
FIG. 5 is a diagram showing a conventional recording amplifier circuit.
[0003]
2. Description of the Related Art Conventionally, there is a magnetic recording apparatus that records information signals on a magnetic tape or the like at a high density using a rotary head. In such a magnetic recording device, a recording signal obtained by modulating an information signal is amplified to a predetermined level by an amplifier circuit and supplied to a rotary head via a rotary transformer. The rotating head records the supplied recording signal on the magnetic tape.
[0004]
At this time, since the above-described rotary transformer has a cutoff characteristic in a low frequency region, the frequency band of the recording signal is usually set to a region not affected by the cutoff characteristic.
[0005]
Here, when information signals having various data rates are recorded by the above-described magnetic recording device, since the information signals having a low data rate are modulated into low-frequency recording signals, the cutoff characteristics of the rotary transformer in the low frequency region are reduced. Therefore, there is a problem that a low-frequency component of the recording signal is cut off.
[0006]
In addition, even when an information signal having a low data rate is not modulated, there is a similar problem when an information signal is recorded using a modulation method having a frequency component up to DC.
[0007]
In order to solve the above-described problem, a magnetic recording apparatus (Japanese Patent Laid-Open No. 4-111202) has been proposed which is provided with an integrating means for compensating a recording signal in a low frequency band before a rotary transformer and an amplifier circuit for amplifying a recording signal. It had been.
On the other hand, as shown in FIG. 5, there is a recording amplifier circuit that performs such signal control using a transistor. In this recording amplifier circuit, when one of the transistors Q1 and Q2 is turned on, the other is turned off, and a current determined by the transistor Q3 flows through the turned on transistor.
[0008]
[Problems to be solved by the invention]
However, in the magnetic recording apparatus described above, after the low-frequency component of the recording signal is emphasized by the integrators 2 and 11, the amplified signal is amplified by the recording amplifiers 4 and 14 having good linearity and the rotary transformer is driven. Even if the power signal is a digital signal, the same performance as when an analog signal is recorded is required, so an amplifier having high speed and good linearity is required. Further, in this case, there is a problem that power efficiency is lower than when signal control is performed using a switching operation of a transistor or the like.
That is, there is a problem that the circuit is expensive, complicated, and has high power.
[0009]
Further, since the above-described recording amplifier circuit performs the switching operation of the transistors Q1 and Q2, the low frequency cutoff characteristic of the rotary transformer cannot be compensated for even if an integrator is provided in the preceding stage.
[0010]
Further, in order to compensate for the low frequency cutoff characteristic of the rotary transformer using the above-described recording amplifier circuit, the current of the recording signal is controlled by the same time constant as the low frequency cutoff characteristic of the rotary transformer and the time constant with respect to the output of the integrator. Therefore, there is a problem in that a current correction circuit for increasing the number of pixels is required, which complicates the circuit configuration.
[0011]
Thus, there has been a demand for a recording amplifier circuit that solves the above-described problem.
[0012]
[Means for Solving the Problems]
Therefore, the present invention provides the following configurations in order to solve the above-described problems.
In a recording amplifier circuit used in a magnetic recording device that records a digital signal supplied to a rotary head via a rotary transformer on a magnetic tape,
A first amplifier and a second amplifier configured to combine a pair of elements for supplying a predetermined current to the rotary transformer based on the digital signal ; Amplifying means configured to turn off the second set of amplifying elements ;
Low-frequency emphasis means for generating a low-frequency emphasis signal based on the inversion cycle period of the digital signal ,
Control means for performing current control such that a current value flowing to the amplification means becomes a predetermined target value based on an output result of the low-frequency emphasis means,
The control unit includes a differential amplifier that controls a current flowing through the amplifier based on an output result of the low-frequency emphasis unit, and a constant current source that keeps the current flowing through the differential amplifier constant. A recording amplifier circuit.

[0013]
【Example】
FIG. 1 is a circuit diagram for explaining the present recording amplifier circuit, FIG. 2 is a diagram for explaining the operation of the present recording amplifier circuit, FIG. 3 is a diagram showing an embodiment of the integrating circuit, and FIG. FIG.
Hereinafter, the recording amplifier circuit according to the present invention will be described with reference to the drawings.
[0014]
As shown in FIG. 1, the recording amplification circuit according to the present invention is a recording amplification circuit used in a magnetic recording apparatus that records a digital signal supplied to a rotary head via a rotary transformer 1 on a magnetic tape. Amplifying means (pulse transformer 2, power supply Vcc, transistors Q1 to Q4) for supplying a predetermined current to the rotary transformer 1 based on the low frequency band of the rotary transformer for generating a low frequency emphasis signal based on the recording signal. A low-frequency emphasizing means (integrating circuit) 3 having an inverse characteristic to the frequency cutoff characteristic, and a current value flowing through the amplifying means (2, Vcc, Q1 to Q4) based on an output result of the integrating circuit 3 becomes a target value. Control means (transistors Q5 to Q7, power supply Vee) for performing current control is provided.
[0015]
A recording signal obtained by modulating a digitized information signal by a modulation circuit (not shown) is supplied to the recording amplifier circuit (recording signal input in FIG. 1). This recording signal is supplied to amplification means (2, Vcc, Q1 to Q4), an inverter 4, and an integration circuit 3, which will be described later, as shown in FIG.
Here, this amplifying means is roughly composed of a pulse transformer 2, a power supply Vcc, and transistors Q1 to Q4. The amplification means rotates a current generated on the secondary side of the pulse transformer 2 by a constant current supplied from the power supply Vcc. This is supplied to the transformer 1 as a recording signal.
[0016]
At this time, for example, if the recording signal is a signal of "Hi", the transistors Q1 and Q3 are turned on. The inverter 4 inverts the "Hi" signal and supplies a "Low" signal to the transistors Q2 and Q4, so that the transistors Q2 and Q4 are turned off.
[0017]
From the power supply Vcc, currents I1 and I4 are supplied to the transistors Q1 and Q4 via the pulse transformer 2, and currents I2 and I3 are supplied to the transistors Q2 and Q3, respectively. When the switching of the transistors Q1 to Q4 is switched as described above, no current flows from the turned off transistors Q2 and Q4, current flows from the transistors Q1 and Q3, and the control means (Q5 to Q7, Vee ).
[0018]
The control means Q5 to Q7 and Vee are transistors Q5 and Q6 to which a current amount (I5 + I6) equal to the current amount (I1 + I3) flowing from the transistors Q1 and Q3, and a current flowing through the transistors Q5 and Q6. It has a transistor Q7 and a power supply Vee which always keep a predetermined amount (I7).
That is, for these current values, I1 + I3 = I5 + I6 = I7
Holds.
Therefore, at this time, the current I1 flows on the primary side of the pulse transformer 2.
[0019]
Here, a constant current does not always flow through the secondary side of the pulse transformer 2 due to the low frequency cutoff characteristic of the rotary transformer 1 at this time.
If a constant current corresponding to the "Hi" recording signal does not flow through the rotary transformer 1 as described above, no current is supplied to the rotary head, and no recording signal is recorded on the magnetic tape. For example, at the time of reproduction, a reproduction signal cannot be obtained even if the rotating head scans on the magnetic tape thus recorded. That is, the information of the recording signal at this time is lost.
Therefore, the following operation is performed in order to always supply a constant current to the rotary transformer 1.
[0020]
For example, the recording signal (shown in FIG. 2A) is supplied to the control means Q5 to Q7, Vee via the integrating circuit 3 having the characteristic opposite to the low frequency cutoff characteristic of the rotary transformer 1. You. The integration circuit 3 performs, for example, RC integration of the recording signal supplied by the integration circuit shown in FIG. 3 to obtain a signal shown in FIG. 2B as a predetermined target value. At this time, the relationship between the gain and the frequency of the rotary transformer 1 and the integrating circuit 3 is as shown in FIG.
[0021]
The output of the integration circuit 3 is supplied to the control means Q5 to Q7 and the Vee transistor Q5. At this time, the transistors Q5 and Q6 form a differential amplifier, and the current I6 decreases as the current I5 increases, based on the relationship between the current values described above.
That is, the current I1 increases as the current I5 increases, and the current I3 decreases as the current I6 decreases.
[0022]
Thus, as the current I1 increases, the current flowing through the pulse transformer 2 increases, so that the current supplied to the rotary transformer 1 provided on the secondary side of the pulse transformer 2 increases. The integration circuit 3 increases the current I5 flowing through the transistor Q5 according to the low frequency cutoff characteristics of the rotary transformer 1, thereby increasing the current I1. Therefore, the integration circuit 3 records the current in accordance with the low frequency cut off by the rotary transformer 1. The signal can be compensated.
[0023]
Here, the present recording amplifier circuit has an independent switch circuit that switches the recording currents I1 and I2 supplied to the rotary head at high speed in accordance with recording signals (“Hi” and “Low” signals). Although it was originally necessary to provide a compensation circuit for compensating the low-frequency cutoff characteristic of the rotary transformer in each switch circuit, in particular, the above-mentioned amplification means 2, Vcc, the current I5 supplied from Q1 to Q4, Since I6 is maintained at the predetermined amount I7 via the differential amplifiers (transistors Q5 and Q6), only one compensating circuit (or the integrating circuit 3 as low-frequency emphasizing means) is required.
That is, a recording amplifier circuit with a simple configuration can be realized.
[0024]
In addition, since the present recording amplifier circuit is configured as described above, the amplitude of the head alternating current (recording current having a different current direction) flowing to the rotary head that compensates for the low frequency cutoff characteristic can be kept constant. The low frequency cutoff characteristics of the rotary transformer can be effectively compensated.
[0025]
Note that, for example, even when a “Low” recording signal is supplied to the present recording amplifier circuit, similarly,
I2 + I4 = I5 + I6 = I7
Is satisfied, it is needless to say that the recording signal can be compensated according to the low frequency cut off by the rotary transformer 1 as described above.
[0026]
In this recording amplifier circuit, since the recording signal in which the low frequency cutoff characteristic of the rotary transformer is compensated by using the switching operation of the transistor is obtained, the pulse transformer and the transistor constituting the amplifying means must be compatible with high-speed operation. Needless to say, the high-speed operation of the recording amplifier circuit can be further performed simply by replacement.
[0027]
Therefore, the present recording amplifier circuit is not limited to a special type among various pulse transformers and transistors.
[0028]
In this embodiment, the operation of the transistors is described as ON and OFF for convenience of explanation. However, for example, when one transistor is turned ON, the other transistor is not completely turned OFF and is weak. Needless to say, a state in which current flows may be used.
[0029]
【The invention's effect】
As described above, according to the configuration of the first aspect of the present invention, there is provided a control unit for performing current control so that a current value flowing through the amplification unit becomes a target value based on an output result of the low-frequency emphasis unit. Therefore, it is not necessary to use high-speed and high-linearity amplifying means, so that the conventional problems of high cost and poor power efficiency are solved, and the recording signal in which the low-frequency cutoff characteristic of the rotary transformer is compensated by a simple configuration. Is obtained.
[0030]
In particular, the control unit includes a differential amplifier unit that controls a current flowing through the amplifier unit based on an output result of the low-frequency emphasizing unit, so that a signal having a target value is supplied to one of the inputs flowing through the differential amplifier unit. The low-frequency cutoff characteristic of the rotary transformer can be compensated for by simply inputting it, so that the amount of current flowing through the switch circuits constituting the recording amplifier circuit is not entirely controlled, and the low-frequency cutoff of the rotary transformer is realized by an inexpensive configuration. There is an effect that characteristics can be compensated.

[0031]
In addition, by providing a constant current source in which the current flowing through the differential amplifying means is always constant, the current flowing through the amplifying means is controlled only by the output result of the low-frequency emphasizing means, so that the low-frequency cutoff characteristic of the rotary transformer Is compensated, the amplitude of the head alternating current flowing through the rotary head can be kept constant, so that the low frequency cutoff characteristic of the rotary transformer can be effectively compensated.
[Brief description of the drawings]
FIG. 1 is a circuit diagram for explaining the present recording amplifier circuit.
FIG. 2 is a diagram for explaining the operation of the present recording amplifier circuit.
FIG. 3 is a diagram illustrating an embodiment of an integration circuit.
FIG. 4 is a diagram for explaining low-frequency emphasis means.
FIG. 5 is a diagram illustrating a conventional recording amplifier circuit.
[Explanation of symbols]
1 rotary transformer 2 pulse transformer (amplifying means)
3. Integrator (low frequency emphasis means)
Q1, Q2, Q3, Q4 Transistor (amplifying means)
Q5, Q6, Q7 Transistor (control means)
Vcc power supply (amplifying means)
Vee power supply (control means)

Claims (1)

In a recording amplifier circuit used in a magnetic recording device that records a digital signal supplied to a rotary head via a rotary transformer on a magnetic tape,
A first amplifier and a second amplifier configured to combine a pair of elements for supplying a predetermined current to the rotary transformer based on the digital signal ; Amplifying means configured to turn off the second set of amplifying elements ;
Low-frequency emphasis means for generating a low-frequency emphasis signal based on the inversion cycle period of the digital signal ,
Control means for performing current control such that a current value flowing to the amplification means becomes a predetermined target value based on an output result of the low-frequency emphasis means,
The control unit includes a differential amplifier that controls a current flowing through the amplifier based on an output result of the low-frequency emphasis unit, and a constant current source that keeps the current flowing through the differential amplifier constant. A recording amplifier circuit.

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