JPH021686Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a tape recorder, and particularly relates to an improvement of its bias oscillation circuit.

[Technical background of the invention and its problems]

Conventionally, as a bias oscillation circuit for a tape recorder, one configured as shown in FIG. 1 is known.

That is, this is an oscillation circuit section consisting of an inductance L connected to a transistor Q as shown in the figure, a capacitor C, resistors _R1 to _R5 , and a diode D.
The OSC is coupled via a transformer T to a magnetic head H serving as a load.

In this case, the primary side of the transformer T is also used as the inductance L component.

However, in such a conventional bias oscillation circuit, since the oscillation circuit section OSC and the magnetic head H are coupled by a transformer T, there is distortion due to loss due to the transformer T and its hysteresis, resulting in non-performance. It had the disadvantage of being efficient.

Furthermore, the configuration shown in FIG. 1 has the problem of being uneconomical because of the large number of parts.

Furthermore, there was also the problem that the value of the bias current supplied to the magnetic head H could not be uniquely set using circuit constants alone.

[Purpose of invention]

Therefore, this idea was made in consideration of the above points, and is not only efficient with no loss or distortion, and economical by reducing the number of parts, but also allows easy setting of bias current. It is an object of the present invention to provide a bias oscillation circuit for a tape recorder which is improved to obtain an extremely good tape recorder bias oscillation circuit.

[Summary of the idea]

That is, the bias oscillation circuit for a tape recorder according to this invention includes an oscillation coil whose one end is connected to a reference potential point, and first and second capacitors whose respective ends are connected to both ends of the oscillation coil in correspondence with each other. a transistor whose bases are commonly connected to the other ends of each of the first and second capacitors and whose collector is connected to a power supply; a first resistor connected between the collector and base of the transistor; The magnetic head is characterized in that it includes a second resistor connected between the emitter of the transistor and the intermediate terminal of the oscillation coil, and supplies a predetermined bias current to the magnetic head from the other end of the oscillation coil.

[Example of idea]

An embodiment of this invention will be described in detail below with reference to the drawings.

In other words, as shown in Figure 2, the transistor
The base of _Q11 is connected to both ends of the oscillation coil _L11 via capacitors _C11 and _C12 .

Here, the connection point between the lower end of the oscillation coil L ₁₁ in the drawing and the capacitor C ₁₂ is grounded.

Further, the collector of the transistor _Q11 is directly connected to the power supply +B and the base via the resistor _R11 , and its emitter is connected to the intermediate terminal of the oscillation coil _L11 via the resistor _R12 . It is connected.

The upper end of the oscillation coil _L11 in the drawing is connected to one end of a magnetic head _H11 serving as a load via a resistor _R13 , and the other end of the magnetic head _H11 is grounded.

Therefore, in the above configuration, if the impedance characteristics (vs. frequency) of the magnetic head H ₁₁ serving as a load are known, and the oscillation voltage V ₀ generated across the oscillation coil L ₁₁ is fixed, then the magnetic head H ₁₁ The bias current i ₀ supplied to is the bias setting resistor R ₁₃
can be determined by the value of

In this case, the oscillation frequency ₀ is is given by

Furthermore, if the impedance of the magnetic head H ₁₁ is _{Z 0 (} however, the frequency is ₀ ), then the bias current i ₀ is given depending on the oscillation voltage V ₀ as follows: i 0 ≈V ₀ /R ₁₃ +Z ₀ It will be done.

In this case, the oscillation voltage V ₀ is V ₀ ≈αC ₁₂ /C ₁₁ +C ₁₂ (where α is a constant), and is determined by the values of the capacitors C ₁₁ and C ₁₂ .

That is, the bias current i ₀ is the capacitor C ₁₁ and C ₁₂
It has the advantage that it can be easily set to an arbitrary value depending on the ratio.

In addition, the bias oscillation circuit described above does not have the oscillation circuit section and the magnetic head connected by a transformer as in the past, so it is efficient without loss or distortion, and the number of parts used can be reduced. Therefore, it has the advantage of being economical.

Furthermore, it has the advantage of contributing to stabilization of temperature characteristics as a high negative feedback.

It goes without saying that this invention is not limited to the embodiments described above and illustrated, and that various modifications and applications can be made without departing from the gist of this invention.

[Effect of idea]

Therefore, as detailed above, according to this invention, it is efficient without loss or distortion, and is not only economical by reducing the number of parts, but also allows easy setting of bias current. It becomes possible to provide an improved and extremely good tape recorder bias circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional bias oscillation circuit, and FIG. 2 is a block diagram showing an embodiment of the bias oscillation circuit according to this invention. Q ₁₁ ... Transistor, C ₁₁ , C ₁₂ ... Capacitor, L ₁₁ ... Oscillator coil, R ₁₁ to _{R 13} ... Resistor,
H ₁₁ ...Magnetic head, +B...Power supply.

Claims (1)

[Scope of utility model registration request] an oscillation coil whose one end is connected to a reference potential point;
A first capacitor and a second capacitor each having one end connected to both ends of the oscillation coil,
and a transistor whose base is commonly connected to each other end of the second capacitor and whose collector is connected to a power supply; a first resistor connected between the collector and the base of the transistor; and a first resistor connected between the collector and the base of the transistor; and a second resistor connected between intermediate terminals of the oscillation coil, and supplying a predetermined bias current to a magnetic head from the other end of the oscillation coil. Oscillation circuit.