JP3202438B2 - I / O device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input / output device provided with a plurality of amplifiers and capable of extracting necessary amplifier outputs by switching with a switch.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of, for example, an input signal switching section of a conventional AV amplifier.
1n are input terminals, 2a, 2b,... 2n are amplifiers for amplifying signals input from the input terminals 1a, 1b,.
a, 2b,... 2n, a switch for selecting and outputting one of the signals amplified by 2n, 4 denotes an amplifier 2a, 2b,.
2n is a power supply for supplying power to 2n.

Next, the operation will be described. Amplifier 2a,
2n amplify the electric signal input from the input terminals 1a, 1b,... 1n to a required voltage, or perform impedance conversion for lowering the line impedance. This amplifier has a plurality (n
), And outputs the necessary amplifier outputs to the switches 3a and 3
b,... 3n to select and output. The power supply 4 supplies a voltage to all of the plurality of amplifiers 2a, 2b,... 2n at the same time.

[0004]

Since the conventional input / output device is configured as described above, the same voltage is supplied from the power supply 4 to both the amplifier that requires output and the amplifier that does not require output. Therefore, all amplifiers are in a normal operating state,
There have been problems such as crosstalk between unnecessary input signals and required input signals, and high power consumption.

The present invention has been made to solve the above problems, and has as its object to reduce the crosstalk between input signals and to obtain an input / output device with low power consumption.

[0006]

Means for Solving the Problems] input and output device according to the present invention comprises a plurality of amplifiers, and a switch for outputting choose necessary among the signal amplified by these amplifiers, each A <br / > a power supply for supplying a power supply voltage to amplifier, e Bei a power supply switching circuit for applying separately to each amplifier and the voltage of the power supply to a predetermined value, the voltage output from the photoelectric Minamotosetsu circuit extracts the output normal voltage to the amplifier, the need not said amplifier for taking out an output is obtained by the that voltage to hold the amplifier while maintaining the input impedance to a high state to a non-operating state.

[0007]

In the input / output device according to the present invention, the power supply voltage applied to the amplifiers not required is reduced by the power supply switching circuit, so that the power consumption can be reduced and the crosstalk between input signals can be reduced. . Further, by lowering the power supply voltage to a voltage slightly higher than the maximum level of the input signal, the input impedance of the amplifier can be kept high even when the amplifier is not operating, and the influence on the preceding circuit can be eliminated. .

[0008]

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 5 denotes a power supply switching circuit which switches the voltage of the power supply 4 to an appropriate value and separately applies the voltage to each of the amplifiers 2a, 2b,... 2n. The same reference numerals are given to the same parts, and the description is omitted.

FIG. 2 shows an example of a circuit constituting the amplifier of FIG. 1. Q1, Q2 and Q3 are transistors, R1 to R6 are resistors, and C1 is a capacitor.

Next, the operation will be described. Amplifier 2a,
2n perform an impedance conversion to amplify an electric signal input from the input terminals 1a, 1b,... 1n to a required voltage or to lower the line impedance from here. A plurality (n) of such amplifiers are provided, and the outputs of the necessary amplifiers are switched 3a, 3b,.
Select and output with 3n. The voltage supplied from the power supply 4 is set to an appropriate value by the power supply switching circuit 5, and is applied separately to each of the amplifiers 2a, 2b,... 2n. The voltage is
Amplifiers that do not extract output are applied with a low voltage that does not destroy the elements of those amplifiers.

For example, as shown in FIG. 1, when only the signal input from the input terminal 1a is to be output, the switch 3
is closed, and the other switches 3b to 3n are opened. In this case, in order to amplify or impedance-convert a required signal, a voltage at which the amplifier 2a operates normally is supplied from the power supply switching circuit 5 to the amplifier 2a to output the signal. On the other hand, since the amplifiers 2b to 2n do not require normal operation, the power supply switching circuit 5 supplies these amplifiers with a low voltage within a range where their elements are not destroyed.

Turn off the voltage supplied to the amplifiers 2b-2n
This is because, for example, when the amplifier is configured by the circuit shown in FIG. 2, the power supply of the unnecessary amplifier is completely turned off.
If the voltage is set to FF (0 V), a large amount of current flows between the base and the collector of the transistor Q1 depending on the magnitude of the input signal, and the transistor Q1 is destroyed. Therefore, in this case, the transistor Q1 is not destroyed by the input signal, and a low voltage in a range where the transistor Q3 does not operate, that is, a voltage slightly higher than the maximum level of the input signal is applied, so that the elements of the amplifier are not destroyed. ,
In addition, it can be set to a state where it does not operate as an amplifier.

More specifically, when the input signal is a video signal of 1V (pp), the transistor Q1 may be damaged when the power supply voltage is 0V, but when the power supply voltage is set to about 1V, the transistor Q1 may be damaged. Destruction of Q1 can be prevented, and no signal is output while transistor Q3 remains cut off.

Therefore, if the normal power supply voltage of this amplifier is 12 V, the power consumption when the power supply voltage is 1 V as described above becomes several tenths of the normal state, Crosstalk around other amplifiers can also be reduced. In this case, the transistor Q1 operates while being imperfect, so that the amplifier can maintain a higher input impedance than when the power supply voltage is set to 0 V, and the influence on the circuit at the preceding stage can be reduced.

[0015]

As described above, according to the present invention, in an input / output device having a plurality of amplifiers, the power supply voltage of an amplifier which is not required is reduced to a range where its constituent elements are not destroyed and do not operate. Since it is configured to lower the power consumption, there is an effect that power consumption is reduced and crosstalk is reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an input / output device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a circuit constituting the amplifier in FIG. 1;

FIG. 3 is a block diagram showing a conventional input / output device.

[Explanation of symbols]

 1a input terminal 1b input terminal 1n input terminal 2a amplifier 2b amplifier 2n amplifier 3a switch 3b switch 3n switch 4 power supply 5 power supply switching circuit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03H 11/34 H03F 1/02 H03H 11/36

Claims (1)

(57) [Claims] [1 claim: a plurality of amplifiers, given a switch for outputting choose necessary among amplified signals, and a power supply for supplying a power supply voltage to each amplifier, the voltage of the power supply in these amplifiers and a power supply switching circuit for applying separately to each amplifier in the value, of the output from the power supply switching circuit
The output voltage is the normal voltage for the amplifier that takes out the output,
For the amplifiers that do not need to take output,
-Keep the amplifier inactive while keeping the dance high
An input / output device characterized by a voltage to be held .