JP2002217765A - Television tuner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a television tuner that uses one kind of printed circuit board so as to normally select a low noise amplifier circuit and a bypass circuit even when a form of switching data to distinguish the magnitude of levels of a television signal differs. SOLUTION: A 1st connection land 15a connected to an output terminal 9a of a changeover circuit 9 and a 2nd connection land 15b to apply a switching voltage to a low noise amplifier 3 and a bypass circuit 12 are placed on a printed circuit board 15 opposed to each other, an input terminal of an inverter 16 to invert a level of the switching voltage is connected to the 1st connection land 15a and an output terminal is connected to the 2nd connection land 15b or both ends of a conductive connector 17 are connected to the 1st connection land 15a and the 2nd connection land 15b, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television tuner, and more particularly to a television tuner capable of changing an operation switching mode between a low noise amplifier and a bypass circuit provided at a television signal input section. .

[0002]

2. Description of the Related Art FIG. 5 shows a main part circuit of a conventional television tuner. The input terminal 21 is connected to an antenna (not shown). The television signal is input to the high-pass filter 22. On the output side of the high-pass filter 22, a low-noise amplifier circuit 23 is provided. The low-noise amplifier circuit 23 has a GaAs FET (gallium arsenide field effect transistor) 23a for amplification, and its gate is connected to a first diode 24a.
Of the high pass filter 2
2 and is grounded by a resistor 25. The source of the GaAs FET 3a is grounded at a high frequency. The drain is a DC cut capacitor 23b.
To the anode of the second diode 26. The cathode of the second diode 26 is grounded by a resistor 27 and is coupled to an output 28.

[0003] To the output terminal 28, a tuning circuit and a high-frequency amplifier circuit for selecting a television signal to be received, a frequency conversion circuit and the like (both not shown) are cascade-connected.

The connection point between the gate of the GaAs FET 23a and the anode of the first diode 24 is connected to the resistor 23.
The terminal c is connected to the output terminal 29a of the switching circuit 29, and the anode of the second diode 26 is also connected to the output terminal 29a of the switching circuit 29 by the resistor 30. In addition, GaAs
The drain of the FET 23a is connected to the resistor 23 from the power supply terminal 31.
d and a voltage is applied in series through the choke inductor 23e.

On the output side of the high-pass filter 22, a bypass circuit 32 provided in parallel with the low-noise amplifier circuit 23 is provided. The bypass circuit 32 operates as a switch element.
It has a channel junction type FET 32 a, and its drain is coupled to the output terminal of the high-pass filter 22 by a DC cut capacitor 33. Also, the source is coupled to the cathode of the second diode 26 by a DC cut capacitor 34. And the gate is the third diode 3
2b is connected to the anode, and the cathode is grounded. Further, a connection point between the gate and the third diode 32b is connected to the output terminal 29a of the switching circuit 29 via the resistor 32c,
The source is also the output terminal 9a of the switching circuit 29 via the resistor 32d.
Connected.

In the switching circuit 29, a switch circuit 29b to which a power supply voltage is applied from a power supply terminal 31 is formed. The switch circuit 29b performs a switching operation based on the switching data D. The switching data D is output from the main body of the television receiver, and corresponds to the level of the television signal input to the input terminal 21. When the level of the television signal is low, a high-level (power supply voltage) switching voltage is output to the output terminal 29a according to the switching data D at that time, and when the level of the television signal is high, the switching data D at that time is output. A low level (ground potential) switching voltage is output.

Therefore, when the level of the television signal is low, the first and second diodes 24 and 26 are turned on, and a bias voltage is applied to the gate of the GaAs FET 23a. Therefore, the television signal is amplified by the low noise amplifier circuit 23 and output to the output terminal 28. At this time, the junction type FET 32 a is cut off because the gate voltage is lower than the source voltage, and the television signal does not pass through the bypass circuit 32.

On the other hand, when the level of the television signal is high, the junction FET 32a has a source voltage and a gate voltage equal to each other, so that the drain and the source are conductive, and the television signal passes through the bypass circuit 32. And outputs it to the output terminal 28. At this time, the first and second diodes 24 and 26 are turned off, and the GaAs FET is turned off.
Since no bias voltage is applied to the gate of 23a, the television signal is neither amplified nor passed by the low noise amplifier circuit 23.

Therefore, the input television signal is
When the level is low, the signal is amplified by the low noise amplifier circuit 23 and output to the output terminal 28. When the level is high, the signal is passed through the bypass circuit 32 without amplification and output to the output terminal 28.

[0010]

By the way, the switching circuit 2
9 is set by the manufacturer of the television receiver, the format is not uniform. For this reason, the switching voltage at the output terminal 29a of the switching circuit 29 may be low when the level of the television signal is low and high when the level is high. Then, the operation of the low-noise amplifier circuit 23 and the bypass circuit 32 operate in reverse to the level of the television signal. In order to solve this problem, it is necessary to separately design circuits for operating the low-noise amplifier circuit 23 and the bypass circuit 32 properly in accordance with the format of the switching data. Since the types of printed circuit boards on which the above circuits are mounted increase, there is a problem that production management becomes complicated.

Therefore, the television tuner of the present invention uses a single type of printed circuit board to provide a low-noise amplifier and a bypass circuit, even if the format of the switching data for distinguishing the level of the television signal is different. The purpose is to enable normal switching.

[0012]

According to the present invention, as a means for solving the above-mentioned problems, a low-noise amplifier for amplifying an input television signal, and a low-noise amplifier provided in parallel with the low-noise amplifier and passing the television signal are provided. A bypass circuit, a switching circuit that outputs a switching voltage that switches between a high level and a low level according to the level of the television signal, and a print that includes the low-noise amplifier, the bypass circuit, and the switching circuit. A low-noise amplifier circuit and the bypass circuit, one of which is in an operating state and the other is in an inactive state by the switching voltage, and
The operating state and the non-operating state are inverted by the level switching of the switching voltage, and a first connection land connected to an output terminal of the switching circuit is provided on the printed circuit board; A second connection land for supplying to the amplifier and the bypass circuit is provided to face each other,
The input terminal of the inverter for inverting the level of the switching voltage is connected to the first connection land and the output terminal is connected to the second connection land, or both ends of the conductive connection body are respectively connected to the first connection land. The connection land was connected to the second connection land.

A third connection land to which a power supply voltage is supplied is provided on the printed circuit board in proximity to the first and second connection lands, and the inverter comprises a PNP transistor. Can be connected to the first connection land, the collector can be connected to the second connection land, and the emitter can be connected to the third connection land.

The first connection lands and the second connection lands are formed in a strip shape and are opposed to each other in parallel, and the third connection lands are positioned at the center of the first connection lands in the strip direction. It was provided on an extension and opposed to the second connection land.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A television tuner according to the present invention will be described with reference to FIGS. FIG. 1 is a circuit of a main part of a television tuner of the present invention. The input terminal 1 is connected to an antenna (not shown), and a television signal is input to a high-pass filter 2. On the output side of the high-pass filter 2, a low-noise amplifier circuit 3 is provided. Low noise amplifier circuit 3
Has a GaAs FET (gallium arsenide field effect transistor) 3a for amplification, its gate is connected to the anode of the first diode 4, its cathode is coupled to the output terminal of the high-pass filter 2, and it is grounded by the resistor 5. You. The source of the GaAs FET 3a is grounded at a high frequency. Further, the drain is coupled to the anode of the second diode 6 via the DC cut capacitor 3b. The cathode of the second diode 6 is grounded by a resistor 7 and is coupled to an output 8. A voltage is applied to the drain of the GaAs FET 3a from the power supply terminal 11 via a resistor 3d and a choke inductor 3e in series.

To the output terminal 8, a tuning circuit for selecting a television signal to be received, a high-frequency amplifier circuit, a frequency conversion circuit and the like are cascaded.

On the output side of the high-pass filter 2, a bypass circuit 12 provided in parallel with the low-noise amplifier circuit 3 is provided. The bypass circuit 12 has an N-channel junction type FET 12a serving as a switch element, and its drain is connected to a high-pass filter
Output terminal. Also, the source is coupled to the cathode of the second diode 6 by the DC cut capacitor 14. The gate is connected to the anode of the third diode 12b, and the cathode is grounded.

The low noise amplifier circuit 3 and the bypass circuit 12
Are mounted on the printed circuit board 15 (see FIG. 2).
A switching circuit 9 that outputs a switching voltage for switching the low-noise amplifier circuit 3 and the bypass circuit 12 between an operation state and a non-operation state is also mounted on the printed circuit board 15. Switching circuit 9
Outputs a switching voltage that switches between a high level and a low level according to the level of the input television signal to the output terminal 9a. The relationship between the level of the television signal and the high / low level of the switching voltage is as follows. Not uniform.

Inside the switching circuit 9, a switching circuit 9b to which a power supply voltage is applied from a power supply terminal 11 is formed. The switch circuit 9b operates according to the switching data D corresponding to the level of the television signal. Switching data D
Is output from a main body of a television receiver (not shown).

On the printed circuit board 15, a first connection land 15a connected to the output terminal 9a of the switching circuit 9, a switching voltage is applied to the low noise amplifier circuit 3, the first and second diodes, and the bypass circuit 12. And a third connection land 15c connected to the power supply terminal 11 are provided. The connection point between the gate of the GaAs FET 3a and the anode of the first diode 4 is connected to the second connection land 15b by the resistor 3c, and the anode of the second diode 6 is also connected to the second connection land 15b by the resistor 10. And the junction type FET1
The connection point between the gate of 2a and the third diode 12b is connected to the second connection land 15b by the resistor 12c,
The source is also connected to the second connection land 15b by the resistor 12d.

First to third connection lands 15a, 15
b and 15c are arranged as shown in FIG. That is,
The first connection land 15a and the second connection land 15b are opposed to each other in a belt shape in parallel with each other.
The third connection land 1 extends on the extension of the center line in the belt-like direction 5a.
5c is provided to face the second connection land 15b.

In an area TR above the first connection land 15a, the second connection land 15b, and the third connection land 15c, an inverter for inverting the level of the switching voltage appearing at the output terminal 9a, for example, FIG. Surface mount type PN shown in 3
In the region R on which the P transistor 16 is mounted or on the first connection land 15a and the second connection land 15b, a cylindrical conductive connection as shown in FIG. 4 for preventing the level of the switching voltage from being inverted. The body 17 is mounted.

Then, for example, when the level of the input television signal is high, the output terminal 9 is switched by the switching data D.
When a high-level switching voltage is output to the output terminal 9a (therefore, a low-level switching voltage is output to the output terminal 9a by the switching data D when the level of the television signal is low), the PNP transistor 16 is set to the region TR. The base terminal B, which is the input terminal of the mounted inverter, is the first connection land 15a, the collector terminal C, the output terminal, is the second connection land 15b, and the emitter terminal E is the third connection terminal 15c. Connecting.

Then, the level of the switching voltage appearing on the second connection land 15b is inverted, and becomes low when the level of the television signal is high, and becomes high when the level of the television signal is low. Then, when the level of the television signal is high, the junction type FET 12a
Since the source voltage and the gate voltage become equal, the connection between the drain and the source becomes conductive, and the television signal passes through the bypass circuit 12 and is output to the output terminal 8. At this time, the first and second diodes 4 and 6 are turned off, and no bias voltage is applied to the gate of the GaAs FET 3a. Therefore, the television signal is not amplified by the low noise amplifier circuit 3 and passes therethrough. Not even.

When the level of the television signal becomes low, the switching voltage of the second connection land 15b changes to a high level, so that the first and second diodes 4, 6 are turned on, and a bias is applied to the gate of the GaAs FET 3a. A voltage is applied. Therefore, the television signal is amplified by the low noise amplifier circuit 3 and output to the output terminal 8. At this time, the junction FET 12a is cut off because the gate voltage is lower than the source voltage, and the television signal does not pass through the bypass circuit 12.

On the other hand, when the low-level switching voltage is output to the output terminal 9a by the switching data D when the level of the input television signal is high (therefore, the switching data D when the level of the television signal is low). Outputs a high-level switching voltage to the output terminal 9a).
The conductive connector 17 is mounted in the region R, and its ends are connected to the first connection land 15a and the second connection land 15b, respectively.

Then, the level of the switching voltage appearing on the second connection land 15b becomes the same as the level of the switching voltage output to the output terminal 9a of the switching circuit 9, and if the level of the television signal decreases, the second level The switching voltage of the connection land 15b also changes to a high level, so that the first and second diodes 4 and 6 are turned on, and a bias voltage is applied to the gate of the GaAs FET 3a. Therefore, the television signal is amplified by the low noise amplifier circuit 3 and output to the output terminal 8. At this time, the junction FET 12a is cut off because the gate voltage is lower than the source voltage, and the television signal does not pass through the bypass circuit 12.

When the level of the television signal increases, the junction type FET 12a becomes conductive between the drain and the source because the source voltage and the gate voltage become equal, and the television signal passes through the bypass circuit 12. And outputs it to the output terminal 8. At this time, the first and second diodes 4 and 6 are turned off, and the GaAs FET 3a
The television signal is neither amplified nor passed by the low noise amplifier circuit 3 because no bias voltage is applied to the gate of the television signal.

[0029]

As described above, according to the present invention, an inverter or a conductive connector is connected to the first and second connection lands according to the mode of the switching voltage output by the switching circuit. When the level of the input television signal is low, the signal can be amplified by the low noise amplifier circuit and output to the output terminal, and when the level is high, the signal can pass through the bypass circuit and be output to the output terminal without amplification. Therefore, even if the mode of the switching voltage output by the switching circuit is different, it can be dealt with by one type of printing.

Further, a third connection land to which a power supply voltage is supplied is provided on the printed circuit board in close proximity to the first and second connection lands, the inverter is formed of a PNP transistor, and the base of the PNP transistor is formed as a third base. Since the connection land can be connected to one connection land, the collector can be connected to the second connection land, and the emitter can be connected to the third connection land, the level of the switching voltage applied to the base can be inverted and output to the collector.

Further, the first connection land and the second connection land are formed in a strip shape and face each other in parallel, and the third connection land is provided on an extension of the center line of the first connection land in the strip direction. Together with the second connection land, the PN
The P transistor and the conductive connector can be mounted on the first to third connection lands in different regions.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a television tuner of the present invention.

FIG. 2 is a pattern diagram of connection lands in the television tuner of the present invention.

FIG. 3 is a plan view of a transistor connected to a connection land in the television tuner of the present invention.

FIG. 4 is a perspective view of a conductive connector connected to a connection land in the television tuner of the present invention.

FIG. 5 is a circuit diagram of a conventional television tuner.

[Explanation of symbols]

 Reference Signs List 1 input terminal 2 high-pass filter 3 low-noise amplifier circuit 3a GaAs FET 3b DC cut capacitor 3c, 3d resistor 3e choke inductor 4 first diode 5, 7, 10 resistor 6 second diode 8 output terminal 9 switching circuit 9a output terminal 9b Switch circuit 11 Power supply terminal 12 Bypass circuit 12a Junction type FET 12b Third diode 12c, 12d Resistance 13, 14 DC cut capacitor 15 Printed circuit board 15a First connection land 15b Second connection land 15c Third connection land

Claims (3)

[Claims] 1. A low-noise amplifier for amplifying an input television signal, a bypass circuit provided in parallel with the low-noise amplifier and passing the television signal, and a level corresponding to the level of the television signal. A switching circuit that outputs a switching voltage that switches to a high level or a low level, and a printed circuit board on which the low-noise amplifier, the bypass circuit, and the switching circuit are mounted. The switching voltage causes one to be in the operating state and the other to be in the non-operating state, and the switching state of the switching voltage is reversed between the operating state and the non-operating state, and the output terminal of the switching circuit is provided on the printed circuit board. And a second connection land for supplying the switching voltage to the low noise amplifier and the bypass circuit. And an input terminal of the inverter for inverting the level of the switching voltage is connected to the first connection land and an output terminal is connected to the second connection land, or a conductive connection is provided. A television tuner, wherein both ends of a body are connected to the first connection land and the second connection land, respectively. 2. A third connection land to which a power supply voltage is supplied is provided on the printed circuit board in proximity to the first and second connection lands, and the inverter comprises a PNP transistor. 3. The television tuner according to claim 2, wherein a base of the television tuner can be connected to the first connection land, a collector can be connected to the second connection land, and an emitter can be connected to the third connection land. 3. The first connection land and the second connection land are in the form of a strip and are opposed to each other in parallel, and the third connection land is positioned at the center of the first connection land in the strip direction. The television tuner according to claim 2, wherein the television tuner is provided on an extension and is opposed to the second connection land.