JPS59198029A - Television tuner circuit - Google Patents

Abstract

PURPOSE:To decrease current consumption by connecting a switch diode to an output terminal of an amplifier so as to use in common a current of a switch circuit and a current of the amplifier. CONSTITUTION:A signal from input terminals A, B passes respectively through band pass filters 1, 2, and is applied to a gate of FETs Q1, Q2 acting like the amplifier. One end of the switch diodes D2, D3 is connected to an output terminal of the FETs Q1, Q2 and the other end of the diodes D2, D3 is connected to switching potentials B1, B2 via load impedances L1, L2. When the switching potential, e.g., B1 is selected, the potential B1 conducts the diode D2 and the FETQ1 and the switching potential B2 reverse-biases the diode D3 and the FET Q2 in this case. Since the current to conduct the switch diode is used in common with the current of the amplifier in this way, the current consumption is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to television tuner circuits.

Structure of the conventional example and its problems FIG. 1 shows an example of a conventional television cheese circuit. In Figure 1, A and B are VHF and UH, respectively.
It is the input terminal of F, and the signals are respectively ■F, U) f
After passing through each filter 1.2 of F, it is supplied to a VHF high frequency amplifier 3 and a tJHF high frequency amplifier 4. One of the signals is selected by the voltages BV and BU applied to the switching terminals of the output signal switch circuit 5 of the high frequency amplifiers 3 and 4. The outputs of the high frequency amplifiers 3 and 4 are applied to the switch circuit 5 in conjunction with the switching signals BV and BU, where ■F, T
One of the JHF signals is selected. The switch circuit 5 consists of resistors R, I R2, R3 (or choke coils) and switch diodes D/
, D21, so that only the switch diode D□ is conductive for the switching voltage BV, and only the switch diode D2 is conductive for the switching voltage BUK. The output of the switch circuit 5 is sent to a broadband frequency mixer 6.
9 frequency converted by the output of the local oscillator 7 controlled by the external DC potential BT, 58 MHz band, 450 MHz.
It is converted into a video intermediate frequency such as MHz band, 900 MHz band, 2 GHz band, etc., and output is supplied from terminal C.

By the way, in order to operate the switch circuit 5 shown in FIG.
For gallium arsenide diodes, good switching characteristics cannot be obtained unless the current is greater than mA, and 10 μm or more, and the drawback is that current consumption increases.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a television tuner circuit with a simple configuration and low current consumption.

Structure of the Invention The television tuner circuit of the first invention includes a first amplifier that amplifies a first signal input manually from a first input terminal, and one end of the television tuner circuit connected to the output end of the first amplifier. a first switch diode connected to the other end of the first switch diode, and one end of the first switch diode connected to the other end of the first switch diode.
a first load coil (or load resistor) that receives a switching potential crab 7Jtl, and a second amplifier that amplifies a second signal that has a different band from the first signal and that is input through the second input terminal. , a second switching diode having one end connected to the output terminal of the second amplifier, and a second switching diode having one end connected to the other end of the second switching diode, and a second switching potential being connected to the other end of the second switching diode. a second load impedance to which is applied, a connection point between the first switch diode and the first load impedance, and a connection point between the second switch diode and the second load impedance; a capacitor, a local oscillator, and a frequency mixer that mixes the signal obtained from one end of either of the coupling capacitors with the output signal of the local oscillator to output a video intermediate frequency signal, The present invention is characterized in that the first switch diode and the second switch diode are selectively rendered conductive by selecting a switching potential of the switch diode.

With this configuration, the entire current of the switch circuit and the amplifier can be shared, and the current consumption can be reduced.

A television tuner circuit according to a second aspect of the invention includes: a third amplifier for amplifying a third signal inputted from a third input terminal, which has a different band from the first and second signals; A third switch diode has one end connected to the output terminal of the amplifier No. 3, and one end of the third switch diode is connected to the other end of the third switch diode, and a third switching potential is applied to the other end of the third switch diode. a second coupling capacitor connected between a third load impedance, a connection point of the third switch diode and the third load impedance, and an input terminal of the first amplifier; A fourth switch diode is inserted between the terminal and the input terminal of the first amplifier, and one end of the fourth switch diode is connected to the first input terminal side of the fourth switch diode. By adding a bias coil (1) to which a fourth switching potential is applied (Iath resistance) and selecting all of the first, second, third, and fourth switching potentials, the first, second, third, and fourth switching potentials are selected. 2
．． The third and fourth switch diodes are all selectively rendered conductive.

With this configuration, it is possible to have the same effect as the first invention and also to compensate for differences in amplification due to differences in bands.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. Second
In the quotient, filters 1, 22 frequency mixer 61 local oscillator 7. Input terminals A, , B, terminal C and external DC potential BT are the same as those in Fig. 1 □ The two signals passed through different bandpass filters l and 21 are:
Coupling capacitance c3. C4'1 are respectively supplied to the first group (G) of field effect transistor Q1+02. Each drain D of the field effect transistor Q1+02 is connected to a switch diode D3. D3
to the anode via the cathode of each switch diode D2. The anodes of D3 are coupled to each other by a capacitor C□, and are connected to terminals to which respective switching potentials B and B2 are applied through load coils □ and L2f:. Only one of the switching potentials B, B2 is selected and makes the switch diode D2 or B3 and the field effect transistor Q or G2 conductive, whereas the unselected potential causes the field effect transistor Q or G2 to conduct.
so that it is reverse biased with respect to the potential of the source S of
The unselected field effect transistor Q□ or G2 and the switch diode D2 or I)3 are made non-conducting and reverse biased. At this time, the switch diode D2.
The reverse bias capacitance of D3 is 0.2 with a GaAs diode.
It is approximately 0.3 pF, and there is a sufficient degree of separation. In this way, the switch diode D2. D3 and field effect trough ') Current reduction is achieved by sharing the current of Q and +Q2. In addition, the operating current of field effect transistors Q1 and G2 is usually 10 mA or more.
, switch diode D3. The switching characteristics of D3 can also be ensured sufficiently. These output signals pass through the wideband frequency mixer 6, and a video intermediate frequency can be obtained from the terminal C.

In FIG. 2, block
, R, is the coupling resistance that provides the AGC potential, and R8゜R
3 is a bias resistor that provides bias. Also, V
, V #'i bias potential "G21 + %2
2UAGCGll G12 indicates the potential, and Ro and C7 are for making the source potential of the transistor 10 DC potential, and C7 has a large capacitance of about 1 μF.

Another embodiment of the invention will be described based on FIG. This example shows the case where a band is added in FIG. 2, and
This is an example in which a method for compensating for differences in gain of field effect transistors that occur depending on the band is considered. In FIG. 3, the symbols 1°2.6, 7. Those marked A, B, C, and BT are the same as those in FIG.

The output of the VHF filter 1 passes through the coupling capacitor C1'f and then the switch diode D1'fr. The switch diode D is made conductive by the switching potential B' applied from the external terminal via the resistor R (a choke coil may also be used).

Non-conduction is controlled. When receiving VHF, the switch diode D becomes conductive. The output of the switch diode D□ is connected to G through the coupling capacitor C3 after being grounded through the resistor R3.
It is supplied to the first gate G0 of the aAs field effect transistor Q. The output of the field effect transistor Q is supplied from the drain D to the next stage through the switch diode D2. A switching potential B is applied to the field effect transistor Q through a switching diode D2 and a choke coil L□ (also has a resistor).

The output signal from this field effect transistor Q is supplied to a frequency mixer 5. On the other hand, (the JHF signal passes through the UHF filter 2 and then passes through the coupling capacitor C4)
It is supplied to the first gate G of the field effect transistor G2. Then, from the drain D of the output field effect transistor Q2 of the field effect transistor Q2, the switch diode D3t- is passed through, and furthermore, the load choke coil L2 (
It is connected to a power source at switching potential B2''! through a resistor (a resistor is also acceptable). During UHF reception, current flows from the power source at switching potential B2' through choke coil L2 and switch diode D3 to field effect transistor Q2. The switch diode D3 is turned on.The UHF signal is supplied from the intersection of the switch diode D3 and the choke coil L2 to the first gate G of the field effect transistor Q through the capacitor C3.

In this case, the switching potential B□' is the switch diode F
Since the DITh cutoff is applied, no VHF signal is applied to the first gate G of the field effect transistor Q.

On the other hand, when receiving ■F, the switching potential B2/ becomes a negative potential, and the switching diode D3 and field effect transistor Q,
In order to cut off the IJHF signal, the IJHF signal is not transmitted to the first gate G of the field effect transistor Q2, but is passed through the switch diode DRO1, which is made conductive by the switching potential B□', and only the F-fold signal is transmitted to the field effect transistor Q2. It is transmitted to the first gate G engineer of Q□. In this way, field effect transistors Q and Q are connected only when receiving tJHF.

The gain difference between ■F and UHF is reduced by passing the signal through a two-stage amplifier to improve the gain of UHF.

D-G of field effect transistor Q1 * G2 in Fig. 3
0 is fed back through a series circuit consisting of resistors R4 and R5 and capacitors C5 and C6, respectively, and this is to ensure frequency characteristics over a wide band. Each gate G□,
G2 includes resistors R8°R3 and R3, each having a high resistance value.
R, R6, R7, R□, bias V throughout.

2.

VG12 "G13" G21 = vG221 VG
23 eIt is designed to be given separately, but this means that each field effect transistor Q at the time of F reception and [F reception]
□, Q2 * It is used to change the operating point of G3, for example i) ■The first goo of the field effect transistor Q when receiving F) The potential of G□'! i Lowering the potential of the first gate G□ of the field effect transistor Q1 during UHF reception is effective in reducing the total current of the field effect transistors Q□ and G2. That is, when receiving LJHF, the amount of current flowing through the field effect transistor Q is reduced.

ii) At the time of UHF reception, the control t of the second gate G2 of the field effect transistors Q and Q is changed to change one AGC delay point of the field effect transistors Q□ and Q2. If the delay point of field effect transistor Q is made faster than field effect transistor Q, AG as block
Overall NF during C delay is improved. Furthermore, the switch diode D does not need to be located within the block X' (it may be placed outside the IC).

In Figure 3, terminal D'
It corresponds to the D band, etc., and after passing through the bandpass filter 8, it passes through the entire coupling capacitor C0, passes through the field effect transistor Q3fc for amplification, and passes from the drain D of the field effect transistor Q3 to the cathode of the switch diode D4, and then from the anode. get the output. When a positive switching potential B3' is supplied through the choke coil L3 (which may also be a resistor), the anode of the switch diode D4 is connected to the anode of the switch diode D2 through the coupling capacitance C0. Depending on these combinations, the switching potential in each band is as follows.

However, 10 is a forward direction. - indicates reverse bias.

Note that the block X' in FIG. 3 was designed assuming an IC circuit, and is particularly effective when using GaAs elements. By implementing an IC circuit, the effects of this invention will be further enhanced.

Effects of the Invention According to the television tuner circuit of the present invention, a reduction in current consumption can be achieved with a simple configuration, and it is highly effective in integrating a high frequency amplifier circuit and a switch circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional example, FIG. 2 is a circuit diagram of one embodiment of the present invention, and FIG. 3 is a circuit diagram of another embodiment of the present invention. 1.2.8 Filter, 6 Frequency mixer, 7...
Local oscillator, D~D4...Diode, Q~Q3...
・・Field effect transistor

Claims (1)

[Claims] A first amplifier that amplifies a first signal that is input in a smaller amount than the input terminal of (])@], and a first amplifier that has one end connected to the output end of the first amplifier. a switch diode, a first load whose one end is connected to the other end of the first switch diode, and a first switching potential is applied to the other end of the load; and a switch diode whose band is different from that of the first signal. a second amplifier that amplifies a second signal input from a second input terminal; a second switch diode having one end connected to the output terminal of the second amplifier; a second load having one end thereof connected to the other end thereof and a second switching potential being applied to the other end of the second load; a connection point between the first switch diode and the load; A coupling capacitor connected between the switch diode and the connection point of the second load, a local oscillator, and a signal obtained from one end of the coupling capacitor is mixed with the output signal of the local oscillator to generate a video intermediate signal. a frequency mixer that outputs a frequency signal, and selectively makes the first and second switching diodes conductive by selecting the first and second switching potentials. (2) a first amplifier that amplifies a first signal input from a first input terminal; a first switch diode having one end connected to the output end of the first amplifier; a first load impedance whose one end is connected to the other end of the switch diode and a first switching potential is applied to the other end of the switch diode; a second amplifier that amplifies a second signal, a second switch diode that has one end connected to the output end of the second amplifier, and a second switch diode that has one end connected to the other end of the second switch diode. a second load impedance to which a second switching potential is applied to the other end of the load impedance; a connection point of the first switch diode and the first load; A first coupling capacitor connected between a connection point of a load impedance and a local oscillator, and a signal obtained from one end of the first coupling capacitor is mixed with the output signal of the local oscillator to generate a video intermediate signal. a frequency mixer that outputs a frequency signal; a third amplifier that amplifies a third signal that is input from a third input terminal and that has a different band from the first and second signals; a third switch diode with one end connected to the output terminal; and a third load with one end connected to the other end of the third switch diode and a third switching potential applied to the other end of the third switch diode. a second coupling capacitor connected between the input terminal of the first amplifier and a connection point of the third switch diode and the third load impedance; a fourth switch diode inserted between the input terminal of the first amplifier; one end of the fourth switch diode is connected to the first input terminal side of the fourth switch diode; and a bias impedance to which a switching potential of the first, second, . By selecting the third and fourth switching potentials, the first. Second. A television tuner circuit in which third and fourth switch diodes are selectively rendered conductive.