JPH01264602A - Magnetic recording and reproducing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording/reproducing device such as a 6-helix Luscan system, and is capable of using a magnetic head with a relatively low Q. Regarding equipment.

[Conventional technology]

In a conventional magnetic recording/reproducing device, for example.

As disclosed in Japanese Patent Laid-Open No. 60-80104, the reproduction signal of the magnetic head is transmitted through a rotary transformer.

It is fed to a regenerative preamplifier and amplified. In the reproduction preamplifier, a capacitor is provided between its input terminal and a ground terminal, and the capacitor and the coil of the magnetic head form a resonant circuit.

The purpose of this resonant circuit is to increase the impedance of the signal source to the reproducing preamplifier through its resonance, improving the N F (No.1se Figure) of the reproducing preamplifier, and improving the frequency characteristics of the FM signal reproduced from the magnetic head. The goal is to equalize the

[Problem to be solved by the invention]

By the way, the wire-wound ferrite magnetic head conventionally used in home VTRs has a relatively high Q (Q3).
, for this purpose, N of the regenerative preamplifier by the above resonant circuit is
F improvement and reproduction equalization were possible.

In contrast, recently wire-wound thin film magnetic heads have been developed for home use.
It is starting to be adopted in R and others. In a thin film magnetic head, the first winding is also formed using thin film technology.

Since the head shape can be made smaller, playback efficiency is high (.

And because there is little stray inductance, it has the characteristic of having a small inductance.

On the other hand, there is a problem in that the first winding pattern cannot be made thicker, so the DC resistance of the first winding becomes high, and the Q decreases (Q Ki 1). Even if resonance is provided, the impedance of the signal source of the regenerative preamplifier cannot be overcome, but the NF of the regenerative preamplifier will deteriorate and the characteristics necessary for regenerative equalization cannot be obtained. There was an order.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording and reproducing apparatus which solves these problems and allows the performance of a reproducing preamplifier to be improved even when a magnetic head with a small Q is used.

[Means to solve the problem]

In order to achieve the above object, one aspect of the present invention is to provide an impedance conversion circuit between a magnetic head and a reproduction preamplifier.

[Function] The impedance conversion circuit consists of a coil and a capacitor. By using a high Q coil as the coil, the Q of the magnetic head becomes high (1 equivalent). Therefore, the Q (2 equivalent) becomes high (2). The Q of the resonance circuit between the magnetic head and the capacitor in the impedance conversion circuit is also high υ.
The impedance of the signal source of the regenerative preamplifier is increased, the NF of the regenerative preamplifier is improved, and good regenerative equalization characteristics are obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a magnetic recording/reproducing apparatus according to the present invention, and numeral 1 indicates a recording medium.

2 is a wire-wound magnetic head, and 3 and 4 are selector switches.

5 is an impedance conversion circuit, 6 is a regenerative preamplifier, and 7 is an impedance conversion circuit.
is an output terminal, 8 is an input terminal, 9 is a recording amplifier, 10 is a rotary transformer, ] 1 is a coil, and 12 is a capacitor.

In the figure, during recording, the changeover switches 3 and 4 are closed to the R side. As a result, the A terminal of the secondary winding of the low retransformer 10 is grounded via the changeover switch 3,
The B terminal is connected via a selector switch 4, 3.

and is connected to the output terminal of the recording amplifier 9. Here, the turns ratio of the primary and secondary windings of the rotary transformer 10 is 1.
:N.

Therefore, the signal input from the input terminal 8 is sent to the recording amplifier 9.
The signal is amplified and supplied to the rotary transformer 10 via the changeover switch 4. In the rotary transformer 10, this signal is current-amplified by n times. The current amplified signal is supplied to the magnetic head 2 and recorded on the recording medium l.

During playback, the selector switches 3 and 4 are closed to the P side.

The A terminal of the secondary winding of the rotary transformer 10 is connected to the impedance conversion circuit 5 via the changeover switch 3.

The Bi terminal is grounded via the changeover switch 4. The impedance circuit 5 includes a coil 11 provided in series between its input terminal and output terminal, and a capacitor 12 provided between the output terminal and the ground terminal.

The signal reproduced from the recording medium 1 by the magnetic head 1 is voltage amplified by n times by the rotary transformer 10, passed through the changeover switch 3 and the impedance/dance conversion circuit 5, and amplified by the reproduction preamplifier 6. The signal is output from the output terminal 7.

FIG. 2 is an equivalent circuit in which the primary side of the rotary transformer 10 at the time of recording of the embodiment shown in FIG. 1 is converted into the secondary side,
13 is an equivalent resistance component of the magnetic head 2, and 14 is the same (equivalent inductance component), and parts corresponding to those in FIG. 1 are given the same reference numerals.

In the figure, the equivalent impedance due to the equivalent resistance component 13° and equivalent interftance component 14 of the magnetic head 2 is n2 times the actual impedance of the magnetic head 2,
The output current LH of the recording amplifier 9 is 1/n times the current actually flowing through the magnetic head 2. During recording, the selector switch 3 is closed to the R side and the A terminal of the rotary transformer 10 is grounded, so that the load seen from the recording amplifier 9 is only the magnetic head 2.

This is the same as the prior art described above.

Figure 3 shows the circuit configuration during playback of Figure 1, 6D,
t5 is a coupling capacitor, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In the figure, in the reproducing preamplifier circuit 6, transistors Ql and Q2 constitute a cascode amplifier, and the output thereof is outputted from an output terminal 7 via an emitter follower which also serves as a transistor Q3. Further, negative feedback of the DC bias is performed via the resistor R1.

The equivalent circuit of this circuit at the time of reproduction is shown in FIG. In the figure, the resistance component 13° and the inductance component 14 of the magnetic head 2 are the equivalent resistance component 2 and the equivalent inductance component converted to the secondary side of the rotary transformer 10 (FIG. 1), and -eHr and eN are the rotary transformers, respectively. 1
Equivalent noise voltage 1 of the magnetic head 2 converted to the secondary side of 0
is the equivalent noise voltage. This noise component eN is generated by the equivalent resistance component 13 of the magnetic head 2. Resistance value RH1 of these equivalent resistance components 13 Equivalent inductance component 1
The inductance values I and H of 4 are actually n2 times, and the 1 equivalent output signal voltage eH and equivalent noise voltage eN are n times the actual values.

In FIG. 4, the magnetic head 2 and the impedance conversion circuit 5 form a resonant circuit.

The Q of this resonant circuit is determined by the sum of the impedances (Li2 + L8) of the equivalent inductance component 14 of the magnetic head 2 and the coil 11 of the impedance conversion circuit 5, and the resistance value RH of the equivalent resistance component 13 of the magnetic head 2. The resonant frequency is the sum of this impedance (LH+L8
) and the capacitance C8 of the capacitor 12 of the impedance conversion circuit 5. Output signal e of magnetic head 2
H, the noise component eN resonates with the Q and resonant frequency in this resonant circuit. The output signal of the magnetic head 2 and the noise component input to the reproduction preamplifier 6 become large near the resonance point of the resonance circuit.

In this way, when the impedance conversion circuit 5 having the coil 11 connected in series between the output terminals is provided between the secondary side of the rotary transformer 10 and the reproduction preamplifier 6, this coil 11 is connected to the magnetic head. 2 and the reproduction preamplifier 6, the Q of the magnetic head 2 becomes high.

Therefore, even if a magnetic head with a smaller Q than a wire-wound thin film magnetic head is used as the magnetic head 2, the coil 1
By increasing the impedance of 1, the Q of the resonant circuit formed with this magnetic head becomes high, and the impedance of the signal source of the reproducing preamplifier 6 is increased, which increases the NF of the reproducing preamplifier 6. is improved, resulting in good reproduction equalization characteristics.

For example, if the Q of the magnetic head 2 is Q=1, then Q=
3, the inductance L8 of the coil 11 of the impedance conversion circuit 5 should be twice the inductance LH of the equivalent impedance component of the magnetic head 2 in FIG. Also.

The resonant frequency of the resonant circuit can be calculated by taking into account the capacitance C8 of the capacitor 12 that is provided with the coil 11.
By appropriately selecting the inductance L8 of υ, the equivalent Q of the magnetic head 2 can be arbitrarily determined.

FIG. 5 shows the resonant frequency of the resonant circuit using a magnetic head with a low Q. 2 shows the frequency characteristics at the input terminal of the reproduction preamplifier 6 with and without the impedance conversion circuit 5, where I and I are the frequencies of the output signal of the magnetic head 2.

■ and ■ are the frequency characteristics of the equivalent resistance component of the magnetic head 2;
IIf is the frequency characteristic of the noise of the regenerative preamplifier 6, 8
.

1), T and U are the cases where the impedance conversion circuit 5 is provided, and i and m are the cases where the impedance conversion circuit 5 is not provided.

When the impedance conversion circuit 5 is not used.

Since the Q of the magnetic head 2 is small, even if a resonant circuit is provided,
The signal source impedance is not flattened as shown by ■' in Fig. 5, and therefore the NF of the regenerative preamplifier 6 deteriorates, and the necessary regenerative equalization characteristics cannot be obtained as shown in 1 in Fig. 5. .

When the impedance conversion circuit 5 is provided as shown in FIG. 1, the reproduction signal of the magnetic head 2 is multiplied by Q at the resonance point, as shown by I in FIG. 5, and the equivalent resistance of the magnetic head 20 is 92
It will be doubled. Also, the C/N of the output terminal of the regenerative preamplifier 2
is degraded by the C/N of the magnetic head 2 plus the noise component of the reproduction preamplifier 2, but near the resonance point, the noise component of the head 2 is much thicker than the noise of the reproduction preamplifier 2. Since this is made so that the C/H is affected by the regenerative preamplifier 2, that is, the regenerative preamplifier 2ONF can be improved.

- When a coil having an inductance sufficiently larger than the inductance of the magnetic head 2 is provided in the impedance conversion circuit 5, the resonance frequency f. can be almost set only by the impedance conversion circuit 5, making it unnecessary to adjust the resonance point as in the conventional case.

Also, the direct current resistance is high like a thin film magnetic head.

If a device with little variation is combined with the impedance conversion circuit 5, Q will remain at an almost constant value and the characteristics necessary for reproduction equalization will be obtained.

FIG. 6 is a circuit diagram showing another embodiment of the magnetic recording/reproducing apparatus according to the present invention during reproduction.

Parts corresponding to those in FIG. 3 are given the same reference numerals.

As shown in the figure, a coil 11 is provided on the primary side of a rotary transformer 10, and a capacitor 12 is provided on the secondary side of the rotary transformer 10 between its terminal A and a ground terminal. Here again, the coil 11 and the capacitor 12 constitute an impedance conversion circuit, and the same effect as in the previous embodiment can be obtained by simply separating this into the primary side and the secondary side of the rotary transformer 10.

However, if you want to obtain the same characteristics as in the case of Figure 3.

The inductance of the coil 11 in FIG. 6 is set to be 17n2 times the interftance of the coil 11 in FIG. 3.

FIG. 7 is a circuit diagram showing still another embodiment of the magnetic recording/reproducing apparatus according to the present invention during reproduction, and parts corresponding to those in FIG. 3 are given the same reference numerals.

This embodiment is a magnetic recording/reproducing device that is not provided with a rotary transformer.

Since the impedance of the magnetic head 2 is not multiplied by n2 by the rotary transformer, the resonant frequency f is the same as in the case of FIG. 3 where the rotary transformer is provided. In order to realize Q and Q, the intance of the coil 11 of the impedance conversion circuit 5 is 1/n2 times that of the case shown in FIG.
The capacitance of the capacitor 12 may be multiplied by the same value <n2.

By the way, it is possible to improve NF by increasing source impedance by increasing the turns ratio of the rotary transformer, but this requires multiple channels in a small diameter cylinder like a home VTR. It is not possible to increase the number of turns of a rotary transformer with a diameter of 11 degrees.Therefore, it is necessary to provide a step amplifier transformer before the reproducing preamplifier.

In the present invention, impedance conversion can be realized with a simple circuit without requiring this transformer. Also.

As shown in FIG. 7, even in a system that does not require a rotary transformer, the present invention can provide a large Q, making it possible to eliminate the need for a step-up transformer.

FIG. 8 is a circuit diagram showing one specific circuit of the entire circuit shown in FIG. 1, 16 and 17 are input terminals for switching control signals, and parts corresponding to those in FIG. 1 are given the same reference numerals.

In the figure, during recording, the switching control signal input to the input terminal 16 is L (low level).

Transistor Q4 of selector switch 4 is off.

Thereby, the output terminal of the recording amplifier 9 is connected to the B terminal of the secondary coil of the rotary transformer 10.

Further, the switching control signal input to the input terminal 17 is at H (high level), and the transistor 12° star Q5 of the changeover switch 3 is turned on. As a result, the A terminal of the secondary coil of the rotary transformer 10 is grounded via the transistor Q, and the impedance conversion circuit 5 of the reproduction system is prevented from becoming a load on the recording amplifier 9. A recording current output from the recording amplifier 9 flows to the magnetic head 2 via the rotary transformer 10.

During playback, the switching control signal input to the input terminal 16 becomes H, turning on the transistor Q4 of the changeover switch 4, and the switching control signal input to the input terminal 17 becomes L, turning the transistor Q5 of the changeover switch 3 on. Turn off. As a result, the B terminal of the secondary coil of the rotary transformer 10 is grounded via the transistor Q4, and the A terminal is connected to the impedance conversion circuit 5. As a result, the recording amplifier 9 of the recording system does not become a load on the magnetic head 2. A reproduction signal from the magnetic head 2 is supplied to a reproduction preamplifier 5 via a rotary transformer 10° impedance conversion circuit 5.

Note that it is also conceivable to provide the changeover switch 3 between the coil 3 in the impedance conversion circuit 5 and the connection point between the coil 3 and the capacitor 5.

If this is done, this coil 1 will become a load on the recording amplifier 9 during recording, which is undesirable.

Further, in the embodiment shown in FIG. 6, a recording-only head and a reproduction-only head are provided, and when the magnetic head 2 is a reproduction-only head, the coil 11 does not become a load on the recording amplifier 9 and there is no problem. If the magnetic head 2 is used for both recording and reproducing purposes, the coil 11 does not serve as a load on the recording amplifier 9, and a recording amplifier with a large dynamic range is required. Therefore, when recording and reproducing via a rotary transformer using a magnetic head for recording and reproducing, such as a home VTR, the coil of the impedance conversion circuit 5 during recording is It is necessary to prevent it from becoming a load on the amplifier 9.

〔Effect of the invention〕

As explained above, according to the present invention, the Q of the magnetic head is
The signal source impedance of the regenerative preamplifier can be increased by increasing the signal source impedance of the regenerative preamplifier to the same side, and even if a magnetic head with low Q is used, the NF of the regenerative preamplifier can be improved. By appropriately setting the characteristics of the magnetic head, it is possible to obtain constant and good reproduction equalization characteristics that are independent of the characteristics of the magnetic head.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the magnetic recording/reproducing apparatus according to the present invention, FIG. 2 is a circuit diagram showing an equivalent circuit during recording in FIG. 1, and FIG. 4 is a circuit diagram showing the equivalent circuit of FIG. 3, FIG. 5 is a comparison diagram of the characteristics of the embodiment shown in FIG. 1 and the prior art, and FIGS. 7 is a circuit diagram showing another embodiment of the magnetic recording/reproducing apparatus according to the present invention, and FIG. 8 is a circuit diagram showing a specific example of the entire circuit configuration of FIG. 1. ■...Recording medium, 2...Magnetic head. 3.4... Selector switch. 5... Impedance conversion circuit. Akira 4 concave, 5 kuni ゐ 7 flash ba

Claims (1)

[Claims] 1. A magnetic recording and reproducing device in which a reproduction signal from a magnetic head is amplified by a reproduction preamplifier, characterized in that an impedance conversion circuit is provided between the magnetic head and the reproduction preamplifier.