JPS5992685A - Integrated signal switching circuit - Google Patents

Abstract

PURPOSE:To obtain a circuit which is suitable to a low power source voltage driving by using a combined transistor (TR) of a differential TR for signal switching and a TR constituting a constant current supply source to produce some difference between DC biases impressed to both bases of the differential TR. CONSTITUTION:When a control signal supplied to a terminal 1 rises above about 0.7V, a TR49 is conducted, the base voltages of TRs 44 and 45 drop to 0V, and the TRs 43 and 54 constitute the constant current supply sources together and resistances 75 and 81. The amount of current of each constant-current supply source is different depending upon the difference in the base voltage of the corresponding TR and when this difference increases, a vertical out of synchronization is caused, so the DC voltage impressed to the bases of TRs 50 and 53 are made different to eliminate the difference between the sink chip voltage and pseudo vertical synchronizing signal voltage of a reproduced video signal appearing at a terminal 9.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention is an integrated circuit suitable for operation at low voltages.

The present invention relates to a switching signal switching circuit.

[Prior art]

In a home-use helical scan VTR, when special playback is performed at a tape speed that is different from that during recording, a pseudo vertical synchronization signal is added to the playback video signal.

By adding this, we are able to obtain a reproduced image without vertical synchronization disturbance.゛Also, image quality deterioration and noise that occur when starting playback, etc.

Many screens have been replaced with black screens to improve usability. Conventionally, these operations are performed by switching a reproduction brightness signal supplied to a terminal 2 into a sync voltage signal 3 in accordance with a control signal supplied to a terminal 1, as shown in FIG. Switch at .

At the same time, it was supplied to terminal B via capacitor 5.

The reproduced color signal is cut off by the switching circuit 7.

Ta. Each output of the switching circuit 4.7 is a luminance value.

The output terminal 9 of the mixer 8 receives a sync signal when a control signal is input.

By outputting the knob voltage and the control signal and unmanned reproduction video signal, addition of a pseudo vertical synchronization signal and reproduction of a black screen at 2° are realized.

And a collection for performing such signal processing.

A switching circuit suitable for the product ratio is shown in Figure 2.

Such circuits are commonly used. Two spears.

51 shows a specific circuit of signal switching circuit 4.7.
0 to 16 are integrated NPN) transistors, 17.18 are integrated NPN) transistors.

Reference voltage source, 19.20 is resistor, 21 is power supply voltage line.

In this case, those that are equivalent or identical to Fang 1 are the same.

The sign is the sign. control supplied to input terminal 1.

When both signals become higher than the reference voltage source 18, the transistor 1° transistor 14 conducts, the transistor 15 turns off, and the voltage signal from the reference voltage source 2 corresponding to the sink chip voltage is applied to the terminal 22 via the transistor 10.11. Output. On the other hand, when the control signal becomes lower than the reference voltage source 1B, the transistor 14 is cut off, the transistor 15 becomes conductive, and the reproduced luminance signal supplied to the input terminal 2 is outputted to the terminal 22 via the transistor 13.12. Ru.

However, the above technology has the disadvantage that it is unsuitable for low voltage operation and cannot reduce the power supply voltage very much.
Especially for machines that require low power.

- It is inconvenient to use in tuple VTRs and the like.

I've started to do that. The above drawbacks are explained below.

I will clarify. Transistor between base and collector.

The bias voltage is reverse biased.

However, this bias voltage is about O■ to normal.

In the direction of the ear, the base collector rapidly changes.

The ability to increase intercalary capacity and rapidly decrease hfe.

It has quality. For this reason, if the base-collector reverse bias is made too low and becomes less than Ov, it may cause waveform distortion in the output signal at high frequencies or increase leakage of input signal components to the output. This may cause other inconveniences.

Therefore, it is necessary to provide a base-collector reverse bias of at least 0.3 .

5 From this point of view, first, in order for the transistor 16 to operate normally as a constant current source, the voltage Y o,xV applied to the resistor 19, that is, the reference voltage source 17, must be set to 1. As an OV,
The collector voltage of the transistor 16 is 1. OV+〇、3
It is necessary to make V = 1.3V or more. With this, 3
.

The reference voltage source 18 should be set to 1.3V + 7V (voltage between transistor 15, nose and emitter) -2.OV.

stomach. Therefore, the control signal needs to be approximately 2.3V, which is slightly higher than the reference voltage source 18 degrees. did.

Once the reference voltage source 3 was 2.3V + 0.3, assuming the reverse bias voltage of the transistor 145 was 0.3V.
V+.

0.7V (Trough Sister 10)VBE) -3,3
V or more [S.

It is necessary to Here we play the brightness signal as normal.

A signal of 1Vp-p is input. Therefore, the most terminal of terminal 22.

High voltage is 3.3V +1. OV becomes -4.3V.

This sword resistance.

A minimum amount of voltage 'k IJ is required across both ends of the resistor 20 in consideration of the voltage fluctuation at the terminal 22 and the minimum amount of voltage 'k IJ nity.

Therefore, the power supply voltage is 4.3V +1. OV=
It is necessary to set it to 5.3V or higher. In reality, taking into consideration the variations in resistance value, transistor VBF, etc.5, it has to be higher. In other words, it has the drawback that the power supply voltage is significantly lowered, making it difficult to use. Particularly when used in a VTR, etc., the C-MOS microprocessor that controls the system operates on a 5-inch power supply, but only 4.

On the other hand, the above-mentioned integrated signal switching circuit does not operate normally and always in 5■, which causes some inconvenience.

[Purpose of the invention]

An object of the present invention is to provide a signal/switching circuit suitable for low power supply voltage driving. 5 [Summary of the Invention] The present invention provides a 9° differential transistor for signal switching and a transistor constituting a constant current source.

Both of the above differential transistors are shared.

By making a difference in the DC bias applied to the base.

This is to compensate in advance for the output offset that occurs due to signal switching.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to Figure 3. spear 3
In the figure, 23 to 55 are integrated transistors, 56 to 84 are integrated resistors, and 85 is a reference voltage source. Parts that are equivalent to or the same as those in Figures 1 and 2 are given the same reference numerals. . In Figure 3, when the control signal supplied to the input terminal 1 becomes approximately 0.7V or more, the transistor 49 becomes conductive and the base voltage of the transistor 44.55 becomes 0V.

Transistors 43, 54 and resistors 75, 81 each have a constant current.

Source 86. Configure B7. Therefore, to input terminal 2.

A thick chip voltage is supplied by the transistor 23.

The reproduced brightness signal whose output level is fixed at a certain voltage (5 voltages, the sum of the reference voltage source 85 and ■BE) is a track.

It is input to the mixer 8 via the meta 41, 42.4 f'Y. Also.

The reproduced color signal 6 has a capacity of 5. Resistor 82 and track.

input to mixer 8 via star 53.52.48'g. .

- When the force control signal falls below approximately 7V, the transistor star 49 is cut off. Since the base voltage of transistors 44, 45 is higher than the base voltage of track stars 43, 54 by the voltage across resistor 69, transistors 44, 45 and resistors 75, 81 are connected to constant current sources 88, 81, respectively.・8
Construct 9. The emitter voltage of transistor 24 thus corresponds to the sink sink tip 15 potential.

mixer 8 through transistors 46, 45, 47
To.

Be input. At this time, transistor 43 becomes normal.

To perform constant current source operation 7, apply voltage to resistor 75.

0.3V, that is, the base voltage of transistor 43 is 10
- Must be 7 or higher.

Also, the average base voltage of the transistor 53 and the transistor.

Since the base voltages of the transistors 50 are the same, it is a direct current.

To cut off the reproduced color signal without changing the intention.

I can do it. 5. In this case, transistor 46 is normally set.

of transistor 46 to operate as a current source.

Because the base voltage y;,) needs to be higher than toV.

Transistor 440 pace voltage across resistor 690.

When the voltage is 0.3V, 1. []V + 0.3V −
1.3V minimum required.

bawl. Therefore, transistor 440 base.

If the inter-collector reverse bias voltage y is 0.3V, the lowest collector voltage of the transistor 45.46 is 1.5V, 5V + 0.7V - 2,3V. Here, as in the conventional example, the reproduced luminance signal is usually 1. '0Vp-
A signal of 1.p is input as the lowest voltage across the resistor 74. oV 15 is required, so the power supply voltage is:
2.3V+.

1oV + toV -4, 3V or more <, conventionally required.

It becomes possible to drive at a low voltage compared to 5.3V or higher. Note that the switching circuit 4 lowers the power supply voltage.

As explained above, the switching circuit 7 has a maximum signal amplitude of 0.7 Vp-p, so the power supply voltage may be lower than that of the switching circuit 4.

By the way, at this time, the currents of the constant current sources 86 and 88.

The amount varies depending on the difference in base voltage of transistors 43 and 44. Transistor base-emitter voltage V
Since BE normally changes according to the collector current, the difference between the voltage difference between vB of transistors 41 and 42 and the voltage difference V between transistors 45 and 46 (V2V
I) occurs. This difference (VtV+) is the sync chip of the reproduced video signal output to terminal 10 (9).

Pseudo vertical synchronous voltage signal added to voltage.

It will be output as a fluctuation of. And this.

When the difference between (Vz and Vf) becomes too large, the reproduced video signal.

The above pseudo-vertical interval is no longer considered to be a 5th period signal at the TV receiver to which it is input, and the TV receiver's vertical signal is no longer recognized.

This results in disturbance in direct synchronization and causes inconvenience.

Now, regarding the switching circuit 4, there is a problem called the vertical disturbance mentioned above.

Although the convenience has been explained, the same can be said about the switching circuit 7.

・　8　・ Therefore, in the present invention, the transistor 50.5! l nobe.

– with a difference in the DC voltage applied to the

Sync chip voltage and pseudo vertical synchronization to main video signal.

This is done to prevent voltage signal differences. Tiger.

The sum of the BIE of the transistor 35 and the voltage across the resistor 650 is equal to the sum of the voltage across the transistor 36 and the voltage across the resistor 660. Therefore, the values of resistors 65 and 66 are appropriate.

If there is a difference, the currents flowing through the resistors 66 and 65 will be different, and a difference will occur on the side B8. So.

The inconvenience of vertical disturbance can be solved by selecting the resistors 65 and 66, taking into account the gain of the mixer 8 and the upper IO error (■2V+) that occurs in the switching circuit 4. . Of course, in integrated circuits, the relative values and precision of elements formed on the same chip are extremely high, and variations in the relative values of transistors and resistors can be made extremely small.

and the variation in the added pseudo vertical sync voltage signal.

is small, and the problem can be solved stably. .

〔Effect of the invention〕

As explained above, according to the present invention, special ,.

Good image quality with no vertical synchronization disturbance during playback can be obtained.

An integrated signal switching circuit can be realized with low power supply voltage.

Ru. This allows for lower power consumption and smaller integrated circuits.

It greatly contributes and in turn uses its integrated circuits.

5 can be achieved by contributing to lower power consumption and miniaturization of VTRs and the like.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional signal switching circuit, Figure 2 is a specific circuit diagram of the main part of a conventional signal switching circuit, and Figure 3 is a circuit showing an embodiment 1O of the signal switching circuit of the present invention. It is a diagram. 1... Control signal 2... Reproduction brightness signal. 4.7...Switching circuit 6...Reproduction color signal. 8... Y&C mixer 9... Playback video signal. 26-55... integrated transistor, 5
56-84...Integrated resistance, 116 1st bacterium Otsuo February L ---J

Claims (1)

[Claims] A reproduction video signal is reproduced according to a control signal. In the circuit that switches to the sync chip voltage of No. 5 Fang 1
emitter of transistor and diode connection. connection to the emitter of the second transistor connected to the Connect the collector of the third transistor to the reading point. Connect the emitter of the transistor in spear 4 to the diode. The collector of the transistor of the tooth 61° is connected to the connection point with the transistor of the tooth 5 which is connected, and the emitter of the transistor of the crucible 73 and the emitter of the transistor of the spear 6 are connected.
Connect one end of the resistor No.1 to the ground, and connect the other end of the resistor No.1 to the ground, and connect the other end of the resistor No.1 to the ground. of transistor pace and spear 4 transistors. Difference in each DC bias voltage applied to the pace. An integrated signal switching device characterized by having: Road.