JPS5810186Y2 - Recording/playback switching circuit for magnetic recording/playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording/playback switching circuit for a magnetic recording/playback device in which switching between recording and playback operations can be performed with a single switch.

An example of a conventional circuit in which a recording circuit and a reproduction circuit are integrated into an integrated circuit (hereinafter referred to as an IC) is shown in FIG.

In other words, 1 is an IC, which includes a recording preamplifier 2.
, a recording head drive amplifier 3, a playback preamplifier 4, and a power amplifier 5 into which the output of the recording preamplifier 2 is input are built-in, and an input terminal 6 of the recording preamplifier 2, a power supply terminal of the recording preamplifier 2 and the recording head drive amplifier 3. 1,
The input terminal 8 of the output/playback preamplifier 4 of the recording head amplifier 3, the output terminal 9 of the playback preamplifier 4, the output terminal 10 of the recording preamplifier 2, and the input terminal 11 of the power amplifier 5.
, a power supply terminal 12 of the reproduction preamplifier 4, a power supply terminal 13 of the power amplifier 5, and an output terminal 14 of the power amplifier 5.

A microphone 15 is connected to the input terminal 6 via a capacitor 29, and a tank circuit 1 is connected to the output/input terminal 8.
A recording/reproducing head 18 is connected through a series circuit of the tank circuit 16 and the capacitor 17, and a capacitor 19 is connected between the connection between the tank circuit 16 and the capacitor 17 and the ground.
A volume regulator 2 in which a capacitor 20 and a sliding terminal are connected to an input terminal 11 via a resistor 21 between an actual output terminal 9 and ground.
2 series circuit, and a capacitor 23 is connected between the output terminal 10 and the input terminal 11, and the power terminal 7 is connected to the fixed contact of the recording/playback selector switch 24.
2 is connected to a fixed contact C of the switch, and a power supply terminal 13 in a housing is connected to a movable contact a of the switch.A power supply 25 and an oscillation circuit 26 are connected to the movable contact a.

Further, an earphone jack 27 is connected to the output terminal 14, and a speaker 28 is connected to the earphone jack 21.

The illustrated state shows the recording state, and the recording preamplifier 2
, the recording head drive amplifier 3, the oscillation circuit 26, and the power amplifier 5 are supplied with power, and the signal from the microphone 15 is amplified by the recording preamplifier 2 and the recording head drive amplifier 3, and is output from the output/input terminal 8 to the recording/playback head. 18
is supplied to perform recording.

On the other hand, the output of the recording preamplifier 2 is inputted to the power amplifier 5 through the output terminal 10 and the input terminal 11, and the output terminal 1
4, the speaker 28 is driven to perform recording monitoring.

For each playback operation, the recording/playback changeover switch 24 is switched and the movable contact a is connected to the fixed contact C.

Then, power is supplied to the playback preamplifier 4, and the output of the recording/playback head 18 is sent to the playback preamplifier 4. Volume adjuster 2
Since the signal is supplied to the power amplifier 5 through 2, the speaker 28 is driven.

However, in this conventional configuration, two fixed contacts are required as the recording/playback selector switch 24, and therefore a slide switch or the like must be used, which is very expensive and requires the use of a slide switch or the like. For example, since it is necessary to attach it to a printed circuit board or the like, it requires a large space and has the disadvantage of being extremely uneconomical and bulky.

The present invention eliminates these conventional drawbacks, and one embodiment thereof will be described below with reference to FIGS. 2 and 3.

In FIG. 2, the same components as those in the conventional configuration in FIG. The output side is connected to the power supply of the reproduction preamplifier 4.

Reference numeral 31 denotes a recording power switch having one circuit and one contact, which is inserted in place of the conventional recording/playback changeover switch.

FIG. 3 shows a specific circuit of the reproduction power switch circuit 30, including a terminal 32 for supplying power to the reproduction preamplifier 4, a terminal 33 for grounding the same, and a terminal 34 connected to the power supply terminal 13. It has a terminal 35 connected to the power supply terminal γ, and has a terminal 32.34.
The collector and emitter of a PNP type transistor 36 are connected between them, and the base Hi resistor 37 of the transistor 36 is connected between the
．． The collector of the NPN type transistor 38 is grounded via the emitter, and the resistor 39 and the collector of the NPN type transistor 40 are connected between the terminal 34 and the ground.

The emitter of the transistor 40 is connected, and the collector of the transistor 40 is also connected to the base of the transistor 38.
A resistor 41 and a collector of an NPN type transistor 42 are connected between the -blade terminal 35 and ground.

A series circuit of an emitter and a resistor 43 is connected, the base of the transistor 42 is connected to the collector, and the collector of the housing is connected to the base of the transistor 400.

Consisting of the above configuration, the housing recording power switch 31
When closed, voltage is applied to the terminal 35 along with the recording preamplifier 2 and the recording head drive amplifier 3, and the transistor 4
Since the voltage divided by the resistor 41.degree. 43 and the diode-connected transistor 42 is applied to the base of the transistor 0, this transistor 40 is turned on, and if the saturation voltage between the collector and base of the transistor 40 is set to a small value.

The transistor 38 is cut off, and therefore the transistor 36 is also cut off, so that no voltage is supplied to the reproduction preamplifier 4, and only the recording circuit is powered on, entering the recording state.

Next, when the recording power switch 31 is turned off to enter the playback state, no voltage is applied to the base of the transistor 40, so the transistor 40 is cut off.

As a result, a bias is applied to the base of the transistor 38 through the resistor 39, and the transistor 38 is turned on. A base current flows through the transistor 36, and this transistor 36 is also turned on, so that power is applied to the reproduction preamplifier 4.

Note that if the collector-base saturation voltage of the transistor 36 is set to a small value, the linearity of the reproduction preamplifier 4 will not be impaired.

Incidentally, in the above embodiment, the recording state is entered when the switch 31 is closed, but the configuration is such that the power supply connections to the recording amplifier system and the playback amplifier system are reversed and the playback state is entered when the switch 31 is closed. You may.

As described above, the mechanical recording/playback selector switch of the present invention has one circuit and one contact, and can be easily configured with a leaf switch, etc., and can be installed in the mechanical section to switch the recording/playback from the printed circuit board. Eliminating the switch would be advantageous in terms of space, and the operating stroke tolerance of the recording/playback selector switch could be greatly reduced, reducing adjustment man-hours and providing significant cost benefits.

In addition, as an IC circuit, the number of terminals can be reduced, and other functions can be added to increase the degree of integration, making it highly effective.It is especially suitable for small tape recorders, etc., and its industrial properties are outstanding. It is something.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional example, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a specific circuit diagram of the main parts. 2... Recording preamplifier, 3... Recording head drive amplifier, 4... Playback preamplifier, 5.
... Power amplifier, 30 ... Playback power switch circuit, 31 ... Recording power switch, 33
, 36, 40...transistor.

Claims (1)

[Scope of utility model registration request] The collector of the PNP transistor is connected to the power supply terminal of the reproduction amplifier or the recording amplifier, the emitter is connected to the main power supply, the base is connected to the collector of the first NPN transistor via a resistor, and the The base of the first NPN transistor is connected to the emitter of the PNP transistor via a resistor and the collector of the second NPN transistor, and the emitters of the first and second NPN transistors are grounded. and the second NP
The base of the N-type transistor is used to switch the power supply of a recording amplifier or a playback amplifier via a resistor.1 Circuit 1
A contact is connected to a fixed terminal of a switch, a movable terminal of this switch is connected to the main power source, and a fixed terminal of the switch is connected to a collector of the PNP type transistor of the playback amplifier or recording amplifier. A recording/playback switching device for a magnetic recording/playback device, characterized in that the magnetic recording/playback device is connected to the power terminal of the other amplifier, and is configured to apply power to either the playback amplifier or the recording amplifier by opening or closing the switch. circuit.