JPS6141469B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an integrated circuit for connecting the audio section of a video recorder to a television receiver.

The use of integrated circuits in the audio section of television receivers is known. For example, 205 in the 1975 edition of the German technical magazine "Radio Engineering (Funklechnik)"
Integrated circuits described on pages 209 to 209
TDA1043 and pages 47 to 2 of ``Lineare Schaltungen'', Volume 2 of the 1974 and 1975 editions of the ``Siemens Databook''.
Integrated circuit TBA120T described on page 55 and
There is a TBA120U.

These integrated circuits generate an audio output signal from a volume control circuit and receive an input signal at an audio frequency amplification circuit. That is, this integrated circuit is used as a connection circuit for a video recorder. This connection is based on the German Industrial Standard (DIN) established in July 1974.
Based on No. 45482, a single line is used to process the audio signal. This audio signal is converted from an audio frequency output signal of the audio circuit to an audio frequency input signal of this audio circuit by an electronic switch activated by a switching voltage generated in the video recorder. Additional circuitry coupled to this integrated circuit is also described on page 55 of the aforementioned "Siemens Data Book". The additional circuit includes an emitter follower circuit, an amplifier circuit, and a capacitor for enhancing the audio frequency output signal and compensating for the de-emphasis of this signal.

An object of the present invention is to provide an integrated circuit capable of eliminating the additional circuit, in particular a capacitor for compensating the attenuation of the audio frequency output signal, and which is incorporated into an audio circuit connected to a video recorder. That's true.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An integrated circuit for connecting a video recorder according to an embodiment of the present invention will be described below with reference to the drawings.

In order to simplify the explanation, in Figure 1,
A demodulator 1 of the audio circuit section of a television receiver and a phase circuit 2 coupled to the demodulator 1 are mainly shown. An audio intermediate frequency signal is applied to the input terminal 3 of this demodulator 1. The output terminal 4 of the demodulator 1 is connected to a volume control circuit LE, a de-emphasis capacitor 5, and the AF of the video recorder 7.
Terminal 6 is connected.

This AF terminal 6 is connected to the audio circuit via line 8.
Connected to the AF output terminal. An electronic switch 10 and an emitter are connected between the AF output terminal 4 and the AF output terminal 9 of the demodulator 1 as a recording circuit, that is, as a signal processing circuit that processes signals from the output terminal 4 to the output terminal 9. A follower circuit 11 is provided, and an emitter follower circuit 12 and an electronic switch 13 are provided as a display circuit, that is, as a signal processing circuit for processing signals from the output terminal 9 to the output terminal 4 direction. These electronic switches 10 and 13 are connected to the video recording and display unit 7.
The opening/closing is controlled by the switching voltage U _s generated at the switch. This switching voltage U _s is designated OV for recording and +12 V for display according to German Industrial Standard (DIN) No. 45482. This switching voltage U _s is applied to the video recording and display unit 7.
It is provided by a power supply 14 and a switch 15 provided inside. When this switch 15 is closed, it indicates the display mode, and when it is open, it indicates the recording mode. In the display mode, this switching voltage U _s cuts off the demodulator 1, as shown by the dashed line extending to the demodulator 1.

FIG. 2 shows a connection circuit according to an embodiment of the present invention for use with the audio circuit TDA1043 described above. As is clear from FIG. 2, this connection circuit is easy to integrate and is inserted between the AF output terminal 4 of the demodulator 1 and the AF output terminal 9 of the audio circuit.

Each electronic switch shown in FIG. 1 includes one half of a differential amplifier circuit having transistors 101 and 131. The collector circuits of these transistors 101 and 131 are provided with diode-coupled transistors 102 and 132. When using a positive supply voltage U, transistors 101 and 131 are PNP transistors, and transistors 102 and 132 are used as compensation transistors.
Consists of NPN transistors. The bases and collectors of these transistors 102 and 132 are coupled, and the emitters are each connected to a resistor 105.
and 135 to the circuit reference potential. In this way, the transistors 103,
The voltage drop required to provide constant current to 134 and 133 is obtained.

The emitters of transistors 101 and 131 are coupled to each other and to double collector transistor 21 via resistor 20 so as to form a constant current source or a current mirror circuit. The emitter of this transistor 21 is coupled to the power supply U, and the base is coupled to one collector.

Transistor 10 belonging to the first electronic switch
At the base of 1, the switching voltage U _s is connected to the resistor 1
6 and a diode 17. The cathode of this diode 17 is the transistor 10
1 base. The base of the transistor 131 belonging to the second electronic switch is connected to a voltage dividing resistor 22 connected between the power supply U and the ground potential.
A constant voltage is received by a voltage dividing circuit including and 23.

The emitter-collector path of switching transistor 103 is coupled to the emitter circuit of emitter-follower circuit 11, and its base is coupled to the base of transistor 102. This switching transistor 103 also forms part of the first electronic switch. This transistor 103
The collector of is coupled to the emitter of the emitter follower circuit 11, and the emitter is coupled to a reference potential via a resistor 106. transistor 103
The current flowing in the collector-emitter path of transistor 101 flows in the collector-emitter path of transistor 101 in the same way as in the case of a constant current source or a current mirror circuit.

Just as the first switching transistor 103 is coupled to the emitter of the emitter follower circuit 11, the second switching transistor 133 is coupled to the emitter of the emitter follower circuit 12. This switching
Transistor 133 forms part of a second electronic switch. The base of this transistor 133 is coupled to the base of a diode-coupled transistor 132, and its emitter is coupled via a resistor 136 to the reference potential point of the circuit.

To compensate for voltage changes caused by the threshold voltage in the base-to-emitter path of transistor 12, the emitter-to-base path of compensation transistor 12' is coupled in series to the base of transistor 12, and the base of transistor 12' is connected to AF.
It is coupled to output terminal 9. The emitter of transistor 12' is also coupled to another collector of double collector transistor 21, the collector of which is coupled to the ground point of the circuit.

In order to perform stable operation in the display mode, it is necessary to generate DC voltages of the same level at the AF output terminal 9 and the AF signal terminal 4. A resistor 18, an auxiliary power supply 19, and a transistor 134 are provided to satisfy this condition. This auxiliary power supply 19 is coupled to the AF output terminal 9 via a resistor 18. The collector-emitter path of the transistor 134 is connected to the auxiliary power supply 1 via a resistor 137.
9 in parallel, the base of transistor 134 being coupled to the bases of transistors 132 and 133. Therefore, the current flowing through the collector-emitter path of this transistor 134 is:
As in the current mirror circuit, it flows in the collector-emitter path of transistor 131. Transistors 12', 21, 101 and 131 are
It is composed of PNP transistors, and the other transistors in FIG. 2 are composed of NPN transistors.

In the display mode, since switching voltage U _s is applied, transistor 131 is conductive and transistors 132, 133 and 134 are turned on.
A current flows through. As a result, transistor 12
and 12' are made conductive, and the AF signal is sent from the AF output terminal 9, which in this case acts as an AF input terminal, to the AF signal output terminal 4 of the demodulator 1 and further to the input terminal of the volume control circuit LE. In this mode of operation, the de-emphasis capacitor 5
are shorted by the low output resistance of the emitter-follower circuit 12.

When no switching voltage is applied, i.e. when the video recorder is set to recording mode, or when the television receiver is operating normally without being connected to the video recorder, transistor 101 is switched on. The transistors 102 and 103 are turned on and current flows through the constant current source or current mirror circuit formed by the transistors 102 and 103. As a result, current flows through the emitter follower circuit 11, and the AF signal is sent from the input terminal 4 to the output terminal 9.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram for explaining the principle of the invention, and FIG. 2 is an explanatory diagram of a connection integrated circuit according to an embodiment of the invention. 1... Demodulator, 4... AF output terminal of demodulator,
5... De-emphasis capacitor, 7... Video recorder, 9... AF output terminal of video recorder, 10... First electronic switch, 11... First
Emitter follower circuit, 12... Second emitter follower circuit, 13... Second electronic switch,
LE……Volume control circuit.

Claims (1)

[Claims] 1. A television receiver having a demodulator whose AF signal output terminal is coupled to a reference potential point via a de-emphasis capacitor and an audio section of a video recorder are connected, and this video In a connection circuit that transfers an AF signal between a recorder and a television receiver using one transfer line, recording is made between an AF signal output terminal of the demodulator and an AF signal output terminal of the audio section of the video recorder. a first electronic switching means and a first emitter-follower circuit forming a signal line, an AF signal output terminal of the demodulator and an audio section of the video recorder;
a second emitter-follower circuit forming a display signal line between the AF signal output terminals and second electronic switching means, the first and second electronic switching means being configured to be switched by a switching voltage generated in the video recorder; An integrated circuit for connecting an audio section of a video recorder to a television receiver, characterized in that it is controlled to switch between a recording mode and a display mode of the video recorder. 2 said first and second electronic switching means together form a differential amplifier circuit, said first electronic switching means being connected to said first transistor;
a second diode-coupled transistor coupled to the collector circuit of the transistor, the second electronic switching means comprising a third transistor and a diode-coupled second transistor coupled to the collector circuit of the third transistor; A switching voltage is applied to the base of the first transistor through a resistor and a diode in series, a constant voltage is applied to the base of the third transistor, and a switching voltage is applied to the base of the first transistor. and the emitter circuit of the second emitter-follower circuit has a base connected to the second and fourth emitter circuits, respectively.
The collector-emitter circuits of the fifth and sixth transistors are coupled to the collector-emitter circuit of the transistor, and in the display mode, the same terminal is connected to the AF signal output terminal of the video recorder and the AF signal output terminal of the demodulator. An auxiliary power supply is coupled to the AF signal output terminal of the video recorder via a resistor so that a DC voltage is generated, and an emitter-collector circuit of a seventh transistor whose base is coupled to the base of the sixth transistor is connected to the emitter-collector circuit of the seventh transistor. An integrated circuit for connecting the audio section of a video recorder to a television receiver as claimed in claim 1, characterized in that it is coupled in parallel to an auxiliary power supply. 3. An integrated circuit for connecting an audio section of a video recorder to a television receiver according to claim 2, wherein an eighth transistor is complementary coupled to the second emitter-follower circuit. .