JPH0782605B2 - Magnetic recording / reproducing circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing circuit for recording / reproducing a recording medium such as a floppy disk, and more particularly to reduction of power consumption suitable for battery driving. .

[Prior Art] Conventionally, magnetic recording in a portable device equipped with a small floppy disk is 5V and 12V for a 5.25-inch type.
It is performed with two V power supplies, and with the 3.5-inch type, it is performed under a single 5 V power supply.

Therefore, in the magnetic recording / reproducing circuit (read / write IC), a single power supply with a voltage of 5V or a voltage of 5V and 12V
It is necessary to operate with two power supplies.

For example, when operating with a single power supply with a voltage of 5V,
In order to sufficiently obtain the effective voltage applied to the head, as shown in FIG. 3, the common terminal 4 provided on the center tap of the coil 2 of the head is directly connected to the power supply. In this case, the switches 6a and 6b represent switching elements in the switching circuit at the time of writing, the constant current source 8 is set so as to pass the write current to the coil 2, and the read obtained at the coil 2 at the time of reading. The signal is applied to the lead circuit.

When the common terminal 4 of the coil 2 is directly connected to the power source as described above, a magnetic recording / reproducing circuit as shown in FIG. 4 is required.

As shown in FIG. 4, the common terminal 4 of the coil 2 is supplied with the power supply voltage Vcc from the power supply terminal 10, and the read signal obtained at the terminals 12a and 12b of the coil 2 by the storage magnetism of the floppy disk is the diode 14 , 16, 18, 20, 22, 24 and resistors 26, 28, 30, 32 to the bases of the transistors 34, 36 forming the preamplifier. Each of the transistors 34, 36 constitutes an emitter follower circuit, and the output level-shifted from the emitter side of the transistors 38, 40 via the diodes 38, 40 is the base of the transistors 42, 44 constituting the next differential amplifier. Added to.

The transistors 42 and 44 are shared by a capacitor 54 connected between terminals 50 and 52 provided via resistors 46 and 48 to form a differential amplifier. It is resistance.

The outputs taken out from the collector sides of the transistors 42 and 44 forming the differential amplifier are added to the bases of the transistors 60 and 62 forming the emitter follower circuit, and the outputs thereof are taken out from the emitter side of the transistors 64 and 66. In addition to the base. Transistors 64 and 66 have resistors 68 and 70
The emitters are commonly used to form a differential amplifier, and the resistors 72 and 74 are load resistors.

The output taken from the collector side of each transistor 64, 66 is added to the bases of the transistors 76, 78 of the output stage circuit composed of the emitter follower circuit, and read signals V ₀₁ , V are output from the output terminals 80a, 80b of each emitter side. _Take out ₀₂ .

And transistors 82, 84, 86, 88, 90, 92, 94, 9
6, 98, 100, 102 are resistors 104, 106, 108,
A constant current source is configured with 110, 112, 114, 116, 118, 120, 122 and 124, and a constant current is passed through the circuit according to the bias voltage VR applied to the terminal 126.

[Problems to be solved by the invention]

Such a magnetic recording / reproducing circuit has a characteristic that the power consumption increases in proportion to the power supply voltage, and the power consumption when operating at a voltage of 12V is 2.4 times (= 12/5).

Therefore, an object of the present invention is to provide a magnetic recording / reproducing circuit that suppresses an increase in power consumption due to an increase / decrease in power supply voltage.

[Means for solving problems]

The magnetic recording / reproducing circuit of the present invention, as shown in FIG.
First amplifier 130 for amplifying the read output of the magnetic head
And a second amplifier 132 for amplifying the output of the first amplifier 130, and a drive voltage for operating the first amplifier 130.
Drive voltage V for operating the second amplifier 132 with respect to V _cc1
with set low (V _cc1> V _cc2) and _cc2, converts the amplified output of the first amplifier 130 to a current, the second amplifier 132 converts the current into voltage compatible to the second amplifier 132 The signal conversion means (voltage / current conversion circuit 134 and current / voltage conversion circuit 136) to be added is installed.

[Action]

According to this structure, lowering the driving voltage V _cc2 of the second amplifier 132 of the output stage requiring a large current, set a high driving voltage V _cc1 of the first amplifier 130 for amplifying an output of the magnetic head Drive voltage V _cc2
Power consumption is suppressed by the reduction of.

〔Example〕

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

FIG. 1 shows an embodiment of a magnetic recording / reproducing circuit of the present invention.

The first amplifier 130 constitutes a pre-stage amplifier that amplifies the reproduction output of the magnetic head. Since this amplifier 130 does not require a large current, its driving voltage V _cc1 is _set to the second amplifier 13.
Set high than the second driving voltage V _cc2, also applies the driving voltage V _cc1 to the common terminal 4 of the coil 2. The output voltage obtained by the amplifier 130 is converted into a current by a voltage / current conversion circuit (V / I) 134 installed as a signal conversion means and transmitted, and the current is a current / voltage installed as a signal conversion means. The voltage is converted into a voltage suitable for the second amplifier 132 by the conversion circuit (I / V) 136 and is applied to the amplifier 132.
In this case, the voltage / current conversion circuit 134 is driven by the high drive voltage V _cc1 like the amplifier 130.

The output of the amplifier 130 obtained by the current / voltage conversion circuit 136 is the amplifier 1 driven by the low drive voltage V _cc2.
Amplified by 32, read signal from output terminals 80a, 80b
It is taken out as V ₀₁ and V ₀₂ .

Thus, the drive voltage V of the amplifier 130 that does not require a large current
_cc1 is increased to increase the dynamic range at the time of writing, drive voltage V _cc2 of the amplifier 132 that requires a large current is decreased, and a voltage / current conversion circuit 134 and a current / voltage conversion circuit 136 are provided between the two. Since the electric current is transmitted, the power consumption can be reduced to about 1/2 without any influence on the transmission of the reproduced read signals V ₀₁ and V ₀₂ .

FIG. 2 shows a specific circuit configuration example of the magnetic recording / reproducing circuit of the present invention.

In this magnetic recording / reproducing circuit, the amplifier 130 is common to the conventional magnetic recording / reproducing circuit shown in FIG. 4, and the voltage / current conversion circuit 134 is composed of the transistors 64, 66 and the resistor 6.
A differential amplifier consisting of 8 and 70, and a transistor 6
The currents flowing through 4 and 66 are taken out by a current mirror circuit composed of a transistor 138 and a transistor 140, and a transistor 142 and a transistor 144 installed on the collector side of each of the transistors 64 and 66.

In addition, the current / voltage conversion circuit 136 includes transistors 146, 14
A resistor 154 as a load is added to the current mirror circuit composed of 8 and resistors 150 and 152, and a transistor 156 and
A resistor 164 as a load is added to the current mirror circuit composed of 158 and resistors 160 and 162 to form transistors 140 and 14
The current flowing out of 4 is converted into voltage. Resistors 154, 16
The voltage obtained at 4 corresponds to the output of the amplifier 130, and
It is suitable for the amplifier 132 driven by the drive voltage V _cc2 .

The amplifier 132 is composed of an emitter follower circuit composed of transistors 76 and 78, and the voltage obtained by the resistors 154 and 164 is applied between the collector and the base to output the read signal V ₀₁ from the output terminals 80a and 80b. , V ₀₂ is taken out.

In this way, the read signal voltage is transmitted by current transmission through the voltage / current conversion circuit 134 and the current / voltage conversion circuit 136, and the read signals V ₀₁ , V _{02 are} output from the output terminals 80a, 80b.
Can be output as, when comparing the circuit shown in this embodiment and FIG. 4, by installing four sets about the current mirror circuit, different drive voltages V _cc1, V _cc2, very easily It is possible to reduce power consumption.

[Effects of the Invention] As described above, according to the present invention, it is possible to extremely easily reduce the power consumption by making the driving voltage different between the portion that consumes a large current and the portion that does not. It is possible to realize low voltage and low power consumption such as battery drive.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a magnetic recording / reproducing circuit of the present invention, FIG. 2 is a circuit diagram showing a concrete circuit configuration example of the magnetic recording / reproducing circuit shown in FIG. 1, and FIG. FIG. 4 is a circuit diagram showing a configuration of a typical magnetic head portion, and FIG. 4 is a circuit diagram showing a conventional magnetic recording / reproducing circuit. 2 ... Coil representing magnetic head, 130 ... First amplifier, 132 ... Second amplifier, 134 ... Voltage / current conversion circuit as signal conversion means, 136 ... Current / voltage as signal conversion means Conversion circuit.

Claims (1)

[Claims] 1. A first amplifier that amplifies a read output of a magnetic head, and a second amplifier that amplifies an output of the first amplifier, and a first amplifier for operating a driving voltage for operating the first amplifier. A signal conversion in which the driving voltage for operating the second amplifier is set low, the amplified output of the first amplifier is converted into a current, the current is converted into a voltage suitable for the second amplifier, and the voltage is applied to the second amplifier. A magnetic recording / reproducing circuit characterized in that means are installed.