JPH0693282B2 - Rotating head type magnetic recording / reproducing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary head type magnetic recording / reproducing apparatus for recording and reproducing a wide band signal, for example, a digitized video signal.

2. Description of the Related Art When a wide band signal, for example, a digitized video signal is recorded and reproduced by using a rotary head type magnetic recording / reproducing apparatus, the resonance frequency due to the inductance of the reproducing system head and the capacitive component from the head to the reproducing amplifier is measured. It is conceivable to provide a regeneration preamplifier on the rotating cylinder in order to make it higher than the required bandwidth of the regeneration system.

FIG. 3 shows a circuit diagram of the Rf system of a rotary head type magnetic recording / reproducing apparatus in which a reproducing preamplifier is provided on a conventional rotating cylinder and recording and reproducing are performed on a recording medium by one head. is there.

Reference numeral 9 is a magnetic head, 10, 12, 15 are switching transistors for switching between recording and reproduction, 11 is a pre-amplifier for reproduction, 13 is a rotary transformer, and 14 is a switch for recording and reproduction.
As shown in FIG. 3, a switching pulse is supplied to each switching element from a and b in which a is high and b is low in the recording state, and a is low and b is high in the reproducing state. It should be noted that the recording / playback switching switch 14 is electrically connected to the recording system circuit when a is high and electrically connected to the reproduction system circuit when it is low. The output impedance of the reproduction preamplifier 11 is about several tens Ω.

The configuration of the conventional example will be described below.

In the recording state, the recording signal is transmitted to the rotary cylinder via the switch 14 and the rotary transformer 13.

In the recording state, the switching pulse of a is high, b is low, the switching transistors 10 and 12 are in the ON state, and the switching transistor 15 is in the OFF state.
As a result, the switching transistors 10 and 12 are respectively grounded, so that the recording signal flows in the direction shown in FIG. 3 and is transmitted to the magnetic head 9.

Next, in the reproducing state, the switching pulses of a and b are a
Is low, b is high, the switching pulses 10 and 12 are in the OFF state, and 15 is in the ON state. As a result, since the switching transistor 15 is grounded, the reproduction signal obtained from the recording medium by the magnetic head 9 flows in the direction shown in FIG. 3, and the reproduction signal amplified by the reproduction preamplifier 11 is rotated by the rotary transformer. 13, through the recording / playback switching switch 14, it is transmitted to the playback system circuit provided on the main body side.

The switching pulse may be supplied onto the rotary cylinder through a slip ring or a rotary transformer.

Problems to be Solved by the Invention However, the above configuration has the following problems.

In the recording state, the switching transistors 10 and 12 are in the ON state and are in the installed state.However, because the impedances of the magnetic head and the rotary transformer are low, the switching transistors 10 and 12 are not sufficiently grounded and one of the recording signals The part leaks into the input stage of the reproduction preamplifier 11 and is amplified. A part of the part is fed back to the rotary cylinder side of the rotary transformer of the rotary transformer 13 to deteriorate the frequency characteristic of the recording system.

When switching between the recording and playback states, the rising and falling edges of the switching pulse cause the high frequency component of the switching pulse to leak between the collector and emitter of the switching transistors 10 and 15 and be amplified by the pre-regenerative amplifier.
A relatively large current flows into the magnetic head. A shown in FIG. 4 indicates that when switching pulses a and b are input,
6 shows a waveform of a current flowing through the magnetic head 9 when a recording signal is not transmitted to the rotary cylinder.

As shown in FIG. 4A, when switching between the recording and reproducing states,
An excessive current may flow through the magnetic head 9 or an erroneous recording signal may be recorded on the recording medium, which may significantly delay the switching speed between the recording and reproducing states.

In the playback system, if the stray capacitance is large due to the performance of the rotary transformer 13 or if the combined inductance value cannot be increased, the broadband playback signal is reduced and the deterioration of the high frequency band is suppressed and transmitted to the main unit side via the rotary transformer. In order to do so, it is necessary to lower the output impedance of the regeneration preamplifier 11, but this is limited by the on resistance of the switching transistor 12.

In view of the above point, the present invention transmits a recording signal and a reproduction signal through a rotary transformer between the rotary cylinder and the main body while minimizing the deterioration of the frequency characteristics, and increases the switching pulse level when switching between the recording and reproduction states. A rotary head type magnetic recording / reproducing apparatus equipped with a pre-reproducing amplifier on a rotary cylinder capable of amplifying leakage of a region component into a switching transistor and suppressing a relatively large current from flowing into the magnetic head. The purpose is to provide.

Means for Solving the Problems The present invention is directed to a magnetic head for recording / reproducing, a pre-reproducing amplifier including an amplifier for amplifying a reproduced signal and a low output impedance buffer, and signal transmission between a rotary cylinder and a main body. Of the rotary transformer, a first switching transistor connected between one end of the magnetic head and a connection point of one end of the rotary transformer and conducting in a reproducing state, the other end of the magnetic head and the amplifier of the pre-regenerative amplifier. A second switching transistor connected between the input stage and the recording stage and connected between the output point of the amplifier of the pre-regenerative amplifier and the input stage of the buffer section and the ground point. The rotating cylinder is provided with a third switching transistor that conducts in the recorded state, and when switching from the reproducing state to the recording state, When the switching transistor of No. 3 is turned on earlier than the second switching transistor and the recording state is switched to the reproducing state, the third switching transistor is set to the second switching transistor.
The rotary head type magnetic recording / reproducing apparatus is characterized in that the switching transistor is cut off with a minute delay after the switching transistor.

Operation According to the present invention, even if a recording signal leaks and is amplified in the input stage of the pre-regenerative amplifier in the recording state by the above-described configuration, it is connected to the output stage of the amplification section of the pre-regenerative amplifier having a relatively high output impedance. When the grounding state is achieved by the switching transistor, the signal returned to the rotary cylinder side of the rotary transformer can be cut, and the deterioration of the frequency characteristic of the recording system can be suppressed.

When switching from the playback state to the recording state, the switching transistor in the output stage of the amplification section of the pre-reproduction amplifier is grounded a little earlier than that timing, and when switching from the recording state to the playback state, it is grounded with a slight time delay. In this state, when switching between the recording and reproducing states, the high frequency component of the switching pulse leaks into the two switching transistors connected to both ends of the magnetic head, is amplified by the pre-reproducing amplifier and returns to generate a relatively large current. , Does not flow into the magnetic head.

The output impedance of the buffer section of the pre-reproduction amplifier can be made extremely low, and even if there are restrictions on the specifications of the rotary transformer, deterioration of frequency characteristics is minimized and the reproduction signal is transmitted through the rotary transformer. Can be transmitted.

Practical Example FIG. 1 shows a circuit system diagram of an Rf system of a rotary head type magnetic recording / reproducing apparatus in an embodiment of the present invention.

In FIG. 1, 1 is a magnetic head, 2, 4 and 5 are switching transistors for switching recording / reproducing, 3 is an amplifying section of a pre-reproducing amplifier, 5 is a buffer section of the pre-reproducing amplifier, 6 is a rotary transformer, and 7 is Indicates a switch for recording / playback. As shown in the first section, a ',
From a ", b ', a switching pulse is supplied in which a', a" is high and b is low in the recording state, and a ', a "is low and b is high in the reproducing state. , A ″ rise time is slightly shorter than a ′, and a ″
The fall time of is set to be slightly shorter than a '. The recording / playback switching switch 7 is electrically connected to the recording system circuit when a'is high, and is electrically connected to the reproduction system circuit when it is low. The output impedance of the reproduction preamplifier buffer unit 5 is less than 1Ω.

The configuration of this embodiment will be described below.

In the recording state, the recording signal is transmitted onto the rotary cylinder via the switch 7 and the rotary transformer 6.
The switching transistors 2 and 4 are grounded in the ON state,
Further, since the output impedance of the pre-reproduction amplifier buffer section 5 is very low, one end of the rotary transformer 6 is in the grounded state, and the recording signal flows in the'direction shown in FIG. 1 and is transmitted to the magnetic head 1.

Next, in the reproduction state, the switching transistor 8 is grounded in the ON state, and the reproduction signal obtained from the recording medium by the magnetic head 9 flows in the direction of ′ and is amplified by the amplification section 3 of the reproduction preamplifier to be stored in the buffer section. 5 is transmitted to the reproduction system circuit provided on the main body side through the rotary transformer 6 and the recording / reproduction changeover switch 7.

As described above, according to the present embodiment, by connecting the switching transistor between the amplification section and the buffer section of the pre-reproduction amplifier, the recording signal is input to the input stage of the amplification section of the pre-reproduction amplifier in the recording state. Even if leaked and amplified, the signal is fed back to the rotary cylinder side of the rotary transformer because it is grounded by the switching transistor at the output stage of the pre-regenerative amplifier with a relatively high output impedance, and the frequency characteristics of the recording system are degraded. Can be kept to a minimum.

Further, as shown in FIG. 2, a'and b are in opposite phases to each other,
Also, a ′ and a ″ are in phase with each other, and the rise time of a ″ is earlier than a ′ by a minute time τ ₁ , and
By delaying the fall time of a ″ by a minute time τ ₂ compared with a ′, leakage of the high frequency component of the switching pulse generated in the switching transistors connected to both ends of the magnetic head has a relatively high output impedance. Since the switching transistor connected to the output stage of the amplification section of the pre-regeneration amplifier is turned on and grounded, as shown in FIG. 2A, it is amplified by the pre-regeneration amplifier and a relatively large current is fed back. As a result, it is possible to prevent an excessive current from flowing through the magnetic head, an erroneous recording signal being recorded on the recording medium, and a significant delay in the switching speed between the recording and reproducing states. .

In addition, in this embodiment, since the buffer section of the pre-regeneration amplifier can be independently lowered, the reproduction signal frequency characteristics can be reduced by making the output impedance very low even if the specifications are limited due to the performance of the rotary transformer. Can be transmitted via a rotary transformer with a minimum deterioration.

In this embodiment, all the switching transistors 2, 4, 8 are npn type transistors, but all pnp type transistors may be used.

Further, in this embodiment, the switching transistors 2, 4,
Although 8 uses the same type of npn type, the same type of pnp type or npn type is used for the switching transistors 2 and 4, the other type is used for the transistor 8, and the switching transistor 2 is the switching transistor 2. It is also possible to input the same switching pulse as above and to input only two kinds of switching pulses on the rotary cylinder.

As described above, according to the present invention, when the pre-reproducing amplifier is provided on the rotating cylinder and recording and reproducing are performed by one head, the frequency characteristics of the recording signal and the reproducing signal are deteriorated through the rotary transformer. Transmission with a minimum of
It is possible to prevent leakage of a high frequency component of a switching pulse into the switching transistor when switching between the recording and reproducing states, which is amplified by the pre-reproducing amplifier to become a relatively large current and flow back to the magnetic head.

[Brief description of drawings]

FIG. 1 is a circuit system diagram showing a main part of an Rf system of a rotary head type magnetic recording / reproducing apparatus of an embodiment of the present invention, and FIG. 2 is a waveform diagram of switching pulses of the embodiment and a current flowing through a magnetic head. Waveform diagram, FIG. 3 is a circuit system diagram showing an essential part of the Rf system of the conventional rotary head type magnetic recording / reproducing apparatus, and FIG. 4 is a waveform diagram of switching pulses and a current waveform diagram flowing in the magnetic head of the conventional example. . 2,4,8 …… Switching transistor, 3 …… Amplification part of pre-regeneration amplifier, 5 …… Buffer part of pre-regeneration amplifier, 6 …… Rotary transformer, 7 …… Recording / playback status changeover switch.

Claims (2)

[Claims] 1. A magnetic head for recording / reproducing, a pre-reproducing amplifier comprising an amplifier for amplifying a reproduced signal and a low output impedance buffer, a rotary transformer for transmitting a signal between a rotary cylinder and a main body, A first connection connected between a connection point of one end of the magnetic head and one end of the rotary transformer and a grounding point, which conducts in a reproducing state
A second switching transistor connected between the other end of the magnetic head and the input stage of the amplification section of the pre-reproduction amplifier and a grounding point, and is electrically connected in a recorded state.
A switching transistor connected between the output stage of the amplifier of the pre-regenerative amplifier and the input stage of the buffer section, and a ground point, which conducts in a recorded state.
And a switching transistor of the above are provided on the rotating cylinder, and when switching from the reproducing state to the recording state, the third
The second switching transistor is turned on earlier than the second switching transistor, and when the recording state is changed to the reproduction state, the third switching transistor is turned off with a slight delay after the second switching transistor. Characteristic rotary head type magnetic recording / reproducing apparatus. 2. The same switching pulse is input to two switching transistors respectively connected to both ends of a magnetic head, wherein the type of a switching transistor which conducts in a recording state and the type of a switching transistor which conducts in a reproducing state are different from each other. The rotary head type magnetic recording / reproducing apparatus according to claim 1.