JPH0488707A - Magnetic amplifier circuit - Google Patents

Abstract

PURPOSE:To attain stable wire by using a voltage of a constant voltage source for a center tap voltage so as to eliminate the effect of power voltage fluctuation on a write current. CONSTITUTION:A circuit generating a center tap voltage VCT consists of a constant current source ICT, a diode D, a center tap reference power supply VCT1, and a transistor(TR) Q11. When a center tap reference power supply VCT1 and a constant current source ICT independently of the fluctuation of the voltage source VCC are employed, the center tap voltage VCT reaches a voltage lower than a voltage VA by a voltage VBE and then the center tap voltage VCT is a voltage independently of the fluctuation of the voltage source VCC.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic amplifier circuit that can output a stable write current even if the power supply voltage fluctuates in a magnetic disk or the like.

[Prior Art] FIG. 2 is a diagram showing an example of a conventional magnetic amplifier circuit.
-FF is a flip-flop for dividing the write data WD, Q7 to Q+a and R3-R5 are transistors and resistors that make up a level shift circuit, and Q1 to Q6 and R1R2 make up a write output circuit. C is the coil, Vcc is the voltage source, Q1□ is the transistor that creates the center tap voltage, ■. 7' is a voltage source that biases the transistor Q+2, VcA is a center tap voltage, IWl+
Iwi is the write output current.

[Problem to be Solved by the Invention] Now, if the voltage source ■cc fluctuates, the center tap voltage VCT will be V cT - V cc - V CE, (Q 1a) However, V CE is the collector voltage of the transistor Q1□. It is expressed as the emitter voltage, and if ■cE (Q1□) = constant, ■oA also changes, and due to the Early effect of transistors Qs and Q4, the collector current of transistors Q, , Q, i.e.,
There was a problem that the write output current fluctuated.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a magnetic amplifier circuit that generates a center tap voltage that does not depend on fluctuations in power supply voltage and suppresses fluctuations in write output current.

Means for Solving the Problems 1 A magnetic amplifier circuit according to the present invention is provided with a constant voltage source that does not depend on fluctuations in power supply voltage, and uses the voltage of this constant voltage source as the center tap voltage.

[Effect]

In this invention, since a voltage from a constant voltage source that does not depend on power supply voltage fluctuations is used as the center tap voltage, the center tap voltage does not fluctuate even if the power supply voltage fluctuates, and stable writing can be performed. I can do it.

〔Example〕

FIG. 1 shows a magnetic amplifier circuit according to the present invention. A is a constant current source, D is a diode, V CTI is a center tap reference power supply, and Qll is a transistor. These constitute a circuit that creates a center tap voltage V (7).
e is the transistor Qs.

This is a resistor connected between the emitter of Q4 and ground, and the same reference numerals as in FIG. 2 indicate the same or equivalent parts.

Now, as shown in the figure, the voltage source is a center tap reference power source that does not depend on cc fluctuations. A. When using a constant current source IC, A.
The voltage at point ■ is VA = VCTI + V! 1z, and the center tap voltage VCT is a voltage lower than ■1 by VBE, so Vct=V^-VBg ”V c + +VBE VBE=VCT,
Center tap voltage Vct is a voltage that does not depend on fluctuations in voltage source VCC. Also, a resistor R, is connected between the emitter of the transistor Q,,Q, and ground.

By connecting Ra, T ΔI/I = ΔV BE/ (-+ Engineering R) However, K
is the Boltzmann constant, T is the absolute temperature, and q is the electron charge.

From the equation, the current fluctuation can be suppressed to a small value. Also, the transistor Q, which creates the center tap voltage ■cT, is
Conventionally, the circuit was constructed using PNP transistors, which resulted in a large area, but since the circuit of the present invention is constructed using NPN transistors, the area occupied within the chip can be reduced.

[Effect of the Invention 1] As described in detail above, this invention provides a constant voltage source that does not depend on power supply voltage fluctuations, and uses the voltage of this constant voltage source as the center tap voltage, so that the write current is equal to or less than the power supply voltage. This has the advantage of being able to perform stable writing without depending on fluctuations in the current.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional magnetic amplifier circuit. In the figure, Q1 to Qll are transistors, R1 to R8
is a resistor, IcT is a constant current source, vcTt is a center tap reference power supply, and D is a diode. Note that the same reference numerals in each figure indicate the same or corresponding parts. Figure 1 Agent: Masuo Oiwa (2 others) D Daisai - Do procedure amendment (voluntary) Figure 1 July 3, 1991 Relationship with the person making the amendment

Claims (1)

[Claims] In a magnetic amplifier circuit that performs writing by applying a center tap voltage to the center tap and passing a write current according to write data, a constant voltage source that does not depend on fluctuations in the power supply voltage is provided, and the voltage of this constant voltage source is set to the center tap voltage. A magnetic amplifier circuit characterized in that it is used for.