JPH0334106A - Magnetic recording and reproduction circuit - Google Patents

Abstract

PURPOSE:To reduce an input conversion noise by eliminating a diode provided at the base of a transistor for differential amplification in a reproduction circuit, providing a diode for leakage prevention between the emitter of the transistor and a current supply path, and providing a diode for bias setting between a magnetic head and a power source. CONSTITUTION:The diodes D11a, D11b and the diodes D12a, D12b for leakage prevention and bias setting connected to NPN transistors Q4a, Q4b and Q5a, Q5b at the amplifying stage of the reproduction circuit are eliminated, and the diodes D4a, D4b, D5a, and D5b that are second pairs of diodes for leakage prevention are provided between the emitter of the amplifier transistor of the reproduction circuit and the current supply path of a differential amplifier, and also, the diode D for bias setting is provided between the magnetic heads Ha, Hb and the power source. By configuring the circuit in such way, the equivalent input resistance of the NPN transistor at the amplifying stage of the reproduction circuit can be reduced, and the input conversion noise due to the spreading resistance of the base can be reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic recording/reproducing circuit, and in particular, it provides an improvement in IK noise due to manual conversion of a reproducing circuit in a magnetic recording/reproducing circuit such as a Flonovi disk drive. It is.

(Prior Art) FIG. 2 shows a conventional magnetic recording/reproducing circuit for a flonovi disk drive having a magnetic head of 2&[[.

In the figure, WRGATE is a signal that instructs the recording state or reproduction state, 5IDE is a signal that selects the magnetic head, and H
a and Hb are magnetic heads, respectively, and WRDATA is a recording signal. 1 is a control circuit for the recording circuit, 2 is a constant current source for the recording circuit, and 3 is a constant current is and control circuit for the reproduction circuit.
+Qz@ is a transistor constituting a recording differential pair corresponding to each magnetic herad, and is controlled by a control circuit l.

Q, ,QS, and Q. , Q3. is a transistor constituting a reproducing amplifier corresponding to each magnetic hand, and is controlled by the control circuit 3 described above.

Next, theory 1 about the operation! II. First, for head selection and switching to recording and playback, the control circuits 1 and 3 that receive the 5IDE (;\ and WRGATE signals)
It will be held in

Next, during recording, the WRGA'rE signal controls the recording circuit control circuit 3 and the recording port? ! ? ! The constant current source 2 for the reproducing circuit is operated, the constant current source for the reproducing circuit, and the control circuit 3 are inoperative, and the reproducing circuit connected to the control circuit 3 is also inoperative. On the other hand, the magnetic head selection in step 1i is performed based on the 5IDE signal, and the head Ha
is selected, the differential transistor Q + b r
The base potential of Q x h is set to the lowest potential, and the differential pair of differential transistors Q, , Q, is made to operate effectively.
Based on T'A signal) and differential! - transistor Q,,,Q
, a turn on and off with each other to enable recording operation. The recording current is determined by a constant current circuit including transistor Q3 and resistor R. Head H (if b is selected, differential transistors Q, , Q, are inactive, Qtb, Qzb
is controlled by the control circuit 1 to operate.

Next, during playback, the WRDA is the opposite of the above recording time.
The constant power supply for the reproduction circuit and the control circuit 3 are operated by the TA signal, and the control circuit 3 for the recording circuit and the constant voltage for the recording circuit are operated. Make M source 2 inactive. A reproducing circuit for reading recorded data in this case will be described next.

If magnetic head +l a is selected, transistor Q. , Q, , Q□ and lit resistor R1, R6°Ro are 3iffi, and the transistor Q a h + Q ? h + Q s h is made non-conductive.

The opposite is true if the magnetic henode Ilb is selected. The minute reproduction output signal from the magnetic head is transmitted through diodes DI+-(D++b) and Dtt-(Dzzb
) through the transistor Q 4- (Q ah )
, Qs - (Qsh), and is amplified here.

The bias of the circuit is transistor Q,,1-b).

Qt-(Q?h> constant current source and diode D,.

(D++b), Dtt-CDrtb), and the base potential of the transistors Qa-(Qo) and Qs-(Qsb) is determined by the power supply voltage (vcc)-diode Dz-
The voltage drop in the I11 direction is (D + z-). On the other hand, the amplification factor of the differential amplifier is Ql-(Qtb),
It is determined by the current determined by Rh-(Rbb) and by Rz and Rx.

In a circuit configured in this way, the transistor Q+- (Qtb) or Ql- (Qtb) is connected to the WR during recording.
A back electromotive force of L·(di/dt) (where i is the current flowing through the transistor Q) is generated at the magnetic head terminal due to the inductance of the magnetic head during the gap where the conduction changes to non-conduction due to the DATA signal. The value of this back electromotive force becomes a problem, especially in the case of devices for Fronbi discs (the value for Fronbi discs is large). value may be reached.

When such a back electromotive force is generated at the magnetic head terminal, this causes the transistor Q. (Qs- or Q
. , Qsb) base-collector abrasive resistor R1 (R3
) to the power supply voltage (vcc). Therefore, to prevent this, diode D*a (
D co, D zh, D 3b) are provided. Also, one differential transistor Q. (Qab
) base-emitter → differential transistor QS-(Qs
It is possible that leakage current occurs in the path of the engineering soter base in b). This is because the breakdown voltage between the emitter and base of the NPN transistor is taken into account, which is as small as about 6V, and in order to suppress the leakage current in this path, a diode D is used.
1, (D,b), and Dtt-(Dzxb), which also serve to determine the bias point of the above-mentioned reproducing circuit.

However, in this conventional circuit, the diode D.

(Dz) and Dtt-(Dzxb), the differential transistor Q. (Q-b)
The equivalent base resistance of Qs-(Qsb) increases. Therefore, the input of the differential amplifier of the regeneration circuit is changed! The noise gets louder,
Possible problems include that recording and reproducing performance deteriorates, and for example, minute signals cannot be reproduced.

Now, if we consider a differential amplifier as shown in Figure 3, -
The equal input noise 11.4 of this differential amplifier for boat fishing is expressed by the fl1 formula. T5' is the base spread resistance of the amplifier stage NPN transistor, and is usually about several ohms.

Δf is the signal bandwidth, Re is the resistance of the transistor itself, and β is the electrical droplet amplification degree.

In the conventional reproducing circuit shown in FIG. 2, the aforementioned γ and ° correspond equivalently to (D, the operating resistance) + (QJ, the base spread resistance). 100μ to diode D1°
The operating resistance when a current is passed through l 00 μA is expressed by the above equation (2).

From the above, the above e. By reducing γ and ゛ in the formula, the equivalent human noise can be reduced.Therefore, it is possible to reduce the equivalent human noise by reducing γ and ゛ in the equation.
If you can delete (Dllm and DllbD,,),
It is considered that the human power equivalent noise level of the reproduction circuit caused by rb' can be reduced.

[Problem to be solved by the invention]

Since the conventional magnetic recording/reproducing circuit is configured as described above, the leakage prevention diode in the reproducing circuit is inserted equivalently in series with the base of the transistor constituting the differential amplifier. There is a problem in that it is difficult to reduce the input conversion noise related to γ1.

This invention was made in order to solve the above-mentioned problems, and provides a magnetic recording and reproducing circuit that can improve the human power equivalent noise caused by r and ° of the differential divider in the reproducing circuit section. The purpose is to obtain.

[Means to solve the problem]

The magnetic recording and reproducing circuit according to the present invention eliminates the diode provided at the base of the differential amplification transistor of the reproducing circuit, and also prevents leakage between the emitter of each differential amplification transistor and the current ('). In addition, a diode for bias setting is provided between the magnetic head and the power supply.

(Function) The magnetic recording/reproducing circuit according to the present invention includes a diode D
By deleting Ila + D+rh and DIga l 01ab, the input conversion noise caused by r and l in the previous equation (1) can be reduced.

〔Example〕

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

FIG. 1 shows a circuit diagram of a magnetic recording/reproducing circuit according to an embodiment of the present invention, and in the figure, the same reference numerals as in the conventional circuit designate the same parts.

In addition, in this embodiment, the leak prevention and bias setting diode D1Dllm + D in the conventional one is used.
zb + D + tb is deleted, and the current of the emitter of the amplification transistor of the regeneration circuit and the differential amplifier ('' (a leakage prevention diode (second diode pair) between the ship channel Da-
, Ds-, Dab, and Dsb, and a bias setting diode D1 is provided between the magnetic head and the current.

Next, the operation will be explained.

In this embodiment, since the diode connected in series to the NPN transistor of the regenerative circuit amplification stage is removed, the equivalent input resistance is reduced. Therefore, the human power fA due to the spreading resistance γ, ゛ of the base of the regeneration 1 river channel: lI M
You can reduce the sound.

In addition, the recording 1 transistor Q! , (Qib) , I
The constant current circuits la (Qqb) and Qsa (Qsb) are inactive, and no leakage occurs from this path. Also, the back electromotive force generated in the magnetic head is generated at both ends of the magnetic head, and the bias setting Since the breakdown voltage of the diode D1 does not occur on the cathode side of the diode D1, the breakdown voltage of the diode D1 may be small.

In the above embodiment, the case where two sets of magnetic heads are provided has been described, but the present invention can also be applied to a case where one or more sets of magnetic heads are provided.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent the counter-electromotive Ti flow generated in the magnetic head during recording, and to reduce the noise caused by the spreading resistance of the base of the reproducing amplifier during reproducing.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a magnetic recording/reproducing circuit according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing a conventional magnetic recording/reproducing circuit, and FIG. 3 is for explaining equivalent human noise of a differential amplifier. FIG. In the figure, 1 is a control circuit for a recording circuit, 2 is a constant current source, 3 is a constant current IS and control circuit for a reproduction circuit, Ha and Hb are magnetic heads, and Q is a constant current source. Q! are the differential transistors of the recording circuit, Q,,Q. is 11 ``DoLIi'!L path amplification transistor, Da
, Ds are leakage prevention IF diodes, and Dl is a bias setting diode during reproduction. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A magnetic recording/reproducing device comprising a plurality of recording/reproducing heads, a recording circuit having the same number of differential transistors as the recording/reproducing heads, and a reproducing circuit having the same number of differential transistors as the recording/reproducing heads. In the circuit, a diode for determining the bias of the reproducing circuit is provided between an intermediate point group of the recording/reproducing head and a power supply path, and a collector pair of the differential amplification transistor of the reproducing circuit and a load resistor. a first pair of diodes for preventing leakage current caused by back electromotive force generated by switching conduction and non-conduction of the differential transistors of the recording circuit; and an emitter pair of the differential amplification transistors of the reproduction circuit. and a second pair of diodes for preventing leakage current caused by back electromotive force generated by switching between conduction and non-conduction of the differential transistor of the recording circuit between the load resistor and the current supply path; A magnetic recording/reproducing circuit characterized in that a reproduction output is taken out from a connection point with a first pair of leakage current prevention diodes.