JPS6025155Y2 - Amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplifier device, and its purpose is to prevent abnormal noise generated when power is turned on with a simple configuration.

Generally, when power is turned on to an amplifier, an impact sound is emitted from a speaker connected to the output end of the amplifier at the same time as the power is turned on, which may cause discomfort to the user.

In order to solve this problem, a conventional arrangement has been made in which, for example, a speaker is connected to the output terminal of the amplifier device with a slight delay after the power is turned on.

However, with this type of configuration, the circuit becomes complicated and manufacturing
It is not very desirable for repair and has the disadvantage of being expensive.

In view of these conventional drawbacks, the present invention provides an amplifying device that uses a small number of parts and can easily prevent the occurrence of the above-mentioned abnormal noise.

An embodiment of the present invention will be described below with reference to drawings of a reproduction amplification section of a tape recorder.

In the figure, a playback signal taken out by a playback head 1 from a magnetic tape (not shown) passes through a preamplifier 2 and a main amplifier 3 in sequence, is amplified, and is output as a playback sound from a speaker 4 connected to the output end of the main amplifier 3. I'm coming.

The preamplifier 2. Power is supplied to the main amplifier 3 from a power source 5 via a power switch 6.

To explain the configuration of the preamplifier 2, one output terminal of the reproducing head 1 is connected to the base of a first stage amplification transistor Q1 via a capacitor C1.

The emitter of the transistor Q1 is grounded via an emitter resistor R1, and the collector is connected to the base of the next stage amplifying transistor Q2.

Further, the collector of the first stage amplification transistor Q□ is connected to the power supply terminal 2a via a collector resistor R2 and a resistor R3.

The end of the resistor R3 on the resistor R2 side is grounded via the capacitor C2, and the low loss B3 and the capacitor C2 constitute an integrating circuit.

Further, a diode D1 is connected in parallel to the resistor R3 constituting the integration circuit so that its cathode is located on the power supply terminal 2a side.

Further, one end of the base resistor R4 is connected to the base of the first stage amplification transistor Q1, and the other end of the base resistor R2 is connected to the emitter of the next stage amplification transistor Q2.

Further, a diode D2 is connected in parallel to the base resistor R4 so that its cathode is located on the base side of the transistor Q1.

The emitter of the next-stage amplification transistor Q2 is grounded via an emitter resistor R3, and the collector thereof is connected to the power supply terminal 2a.

A bypass capacitor C is connected in parallel to the emitter resistor R3.
3 is connected.

The collector of the transistor Q2 is grounded via the capacitor C4 and the volume adjusting variable resistor VR in sequence, and the sliding contact of the variable resistor VR is connected to the output terminal 2b.

In the embodiment described above, when the power switch 6 is turned on, power is supplied from the power supply 5 to the preamplifier 2 and the main amplifier 3.

In this case, power is supplied to the collector of the first-stage amplification transistor Q□ constituting the preamplifier 2 through the collector resistor R2 and an integrating circuit consisting of a resistor R3 and a capacitor C2.

Further, power is supplied to the base of the transistor Q□ from the collector of the transistor Q□ through the base and emitter of the next-stage amplification transistor Q2 and further through a diode D2 connected in parallel to the resistor R1.

In this power supply process, if we assume that the diode D2 is not present and power is supplied to the base of the transistor Q□ via the resistor R4, the resistance value of the resistor R2 is generally large; The time constant of this time constant circuit consisting of resistor R4 and capacitor C1 is larger than the time constant of other time constant circuits, such as the time constant circuit consisting of resistor R3 and capacitor C2, so that the collector side of transistor Q□ reaches a predetermined voltage. After that, a predetermined voltage is applied to the base of transistor Q1.

When such a power supply process is adopted, a so-called switching phenomenon occurs in which when a predetermined base voltage is applied to the transistor Q1, its collector voltage rapidly decreases, and an abnormal sound is emitted from the speaker 4.

However, in the above embodiment, since the diode D2 is connected in parallel to the resistor R4 that supplies power to the base of the transistor Q□, the diode D2 becomes conductive when the power is turned on, and the base of the transistor Q1 is connected with the resistor R4 shorted. Power is supplied to the

Therefore, by the time the collector voltage of the transistor Q□ reaches a predetermined value, a predetermined voltage is already applied to the base of the transistor Q, and the collector voltage does not drop suddenly.

Therefore, generation of abnormal noise from the speaker 4 can be prevented.

Next, a case will be described in which the power to an amplifier in an operating state is temporarily cut off and then immediately turned on again.

In this operation process of shutting off the power and turning it on again, assuming that there is no diode connected in parallel to the resistor R3 that constitutes the integrating circuit, the diode connected to the base of the first stage amplifying transistor Q1 when the power is shut off is assumed to be absent. The charge stored in the capacitor C□ is rapidly discharged from the base of the transistor Q1 to the emitter and then through the resistor R1, and in order to put the transistor Q into a non-operating state, the charge stored in the capacitor C2 constituting the integrating circuit is reduced. is slowly discharged to the power supply terminal 2a side via the resistor R3.

In this way, although the capacitor C1 is rapidly discharged, the capacitor C2 is discharged via the resistor R4, so a relatively long time is required.

This means that although the base voltage of transistor Q quickly drops to zero, the collector voltage gradually shifts to zero from a predetermined voltage.

Therefore, when the power switch 6 is turned on again immediately after turning off the power switch 6 or after a relatively short period of time, the collector voltage of the transistor Q□ has already reached a certain value, so it immediately returns to the predetermined value. When the voltage reaches this voltage, and then a predetermined voltage is applied to the base of the transistor Q, a switching phenomenon occurs in which the collector voltage of the transistor Q1 rapidly decreases as described above, and an abnormal sound is generated from the speaker 4. do.

However, in the above embodiment, since the diode D is connected in parallel to the resistor R3 constituting the integrating circuit, the diode D becomes conductive when the power is cut off, and the capacitor C2
to quickly discharge the charged charge.

Therefore, even if the power is turned on again immediately after the power is turned off, the same power supply process as when the power was turned on for the first time is reproduced, and no abnormal sound is generated from the speaker 4.

In the above embodiment, the resistors R3, R, and the diodes D□,
Although the configuration is such that D2 is connected, a transistor or the like may be used instead of the diode.

In short, any element that has directionality is sufficient.

As explained above, in the amplifier device of the present invention, a directional element is connected in parallel to the resistor that supplies power to the base of the amplification transistor, the resistor that constitutes the time constant circuit connected to the collector side, and controls the power supply to the transistor. This not only prevents abnormal noises that occur when the power is turned on, but also prevents abnormal noises that occur when the power is turned off and then turned on again, making it possible to turn on the power from any state. However, abnormal noises will no longer occur.

Moreover, since it has a simple configuration, it can be implemented at low cost.

[Brief explanation of the drawing]

The drawing is an electrical wiring diagram showing a reproduction amplification section of a tape recorder to which an embodiment of the device of the present invention is applied. 1...Playback head, 2...Preamplifier, 3...Old main amplifier, 4...Speaker, 5...
Song power supply, 6... Song power switch, Q□... Amplification transistor, R2... Collector resistor, C2
, R3... Capacitor and resistor forming the curved integration circuit, R
4...Base power supply resistance, Dl, D2...
··diode.

Claims (1)

[Scope of utility model registration request] Power is supplied to the base and collector of the amplification transistor through resistors, a first integrating circuit consisting of a resistor and a capacitor is connected between the resistor on the collector side and the power supply, and a first integrating circuit consisting of the resistor and capacitor on the base side is connected between the resistor on the collector side and the power supply. In an amplifier in which the emitter side is connected to ground via a resistor, a directional element is connected in parallel to the resistor that supplies power to the base of the transistor in the same direction as the current that normally flows through this resistor. 1. An amplifying device characterized in that a resistor constituting the first integrating circuit is connected in parallel to a directional element in a direction opposite to the current normally flowing through the resistor.