JP2532177Y2 - High frequency integrated circuit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency integrated circuit used for a tuner of a TV or VTR.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a configuration example of a conventional high-frequency integrated circuit and its peripheral circuits. In this figure, 1 is a high-frequency integrated circuit, 2 is a VHF oscillation circuit that outputs a local oscillation signal in the VHF band, 3 is a UHF oscillation circuit that outputs a local oscillation signal in the UHF band, 4 is a U / V switching circuit, By switching and connecting the switch 5 in the VHF oscillation circuit 2 to the VHF selection terminal 5a or the UHF selection terminal 5b, the VHF oscillation circuit 2 and the UHF oscillation circuit 3 are controlled to operate / non-operate.

In the VHF oscillation circuit 2, the transistors Q1 and Q2 constitute a feedback amplification type oscillation circuit, and the emitters are commonly connected. Resistors R1 and R
2 and constant voltage source VA are connected to transistors Q1 and Q2
Is supplied with a base bias voltage. Transistor Q3 and resistors R3 and R4 form a constant current source and have a U / V
The collector voltage of the transistor Q6 of the switching circuit 4 is turned on at a high level and turned off at a low level. The diode-connected transistor Q4 and resistor R5 are provided to prevent a latch-up phenomenon of the high-frequency integrated circuit 1 described later. Further, the high-frequency integrated circuit 1 includes
The _Vcc voltage is applied from the power supply _Vcc to the internal circuit via the power supply terminal 6.

[0004] Further, in the VHF oscillator circuit 2, the tuning control terminal voltage V _T1 for tuning is applied by control circuit (not shown) 7, capacitors C2-C4, the variable capacitance diode D1, a choke coil L1 and the resonant coil L2 Is
A VHF resonance circuit is configured, and the frequency of the local oscillation signal in the VHF band oscillated in the VHF oscillation circuit 2 is varied by the tuning voltage _VT1 applied via the resistor R6.

In the UHF oscillation circuit 3, Q7 and Q
Reference numeral 8 denotes a transistor for high-frequency oscillation and amplification having the same characteristics. A distributed constant line L whose length is set to 1/2 of the wavelength of the local oscillation signal in the UHF band.
3, the variable capacitance diode D2 and the capacitor C5
A UHF resonance circuit is formed, and their values are such that their combined impedance is equivalently inductive in the oscillation frequency band, and the phase difference between the local oscillation signals in the UHF band oscillated in the transistors Q7 and Q8. 180
° is preset.

In the UHF oscillation circuit 3, C6 and C7 are DC blocking capacitors, C8 and C10 are feedback capacitors, and C9 is a temperature compensating capacitor for the output capacitance of the transistors Q7 and Q8. Note that capacitors C8 and C10 having the same characteristics and values are used. 8 is a tuning voltage V _T2 by a control circuit (not shown).
There is a tuning control terminal applied, the frequency of the local oscillation signal of the UHF band to be oscillated in the UHF oscillation circuit 3 is varied by the tuning voltage V _T2 applied through the resistor R17.

Further, in the UHF oscillation circuit 3, the resistors R12 and R13 and the constant voltage source VC supply a base bias voltage to the transistors Q7 and Q8. Transistors Q9 and Q10 and resistors R14 to R16
Constitutes a constant current source, and turns on when the collector voltage of the transistor Q5 of the U / V switching circuit 4 is at a high level and turns off when the collector voltage is at a low level. In the U / V switching circuit 4, R7 is an input resistor, transistors Q5 and Q6 are transistors having a common emitter configuration, resistors R8 to R11 and a constant voltage source VB.
Supplies a base bias voltage to transistors Q5 and Q6.

In such a configuration, when the switch 5 in the VHF oscillation circuit 2 is connected to the UHF selection terminal 5b,
The collector voltage and the base voltage of the transistor Q4 are
It becomes 0V. As a result, the collector voltage of the transistor Q5 of the U / V switching circuit 4 goes high,
The base voltage of transistors Q9 and Q10 in F oscillation circuit 3 rises, and the constant current source including transistors Q9 and Q10 and resistors R14 to R16 turns on. Now, a base bias voltage is applied to each base of the transistors Q7 and Q8 from the constant voltage source VC via the resistors R12 and R13, and a power supply V is applied to each collector of the transistors Q7 and Q8.
_{Since the Vcc} voltage is applied from the _cc via the power supply terminal 6, the UHF oscillation circuit 3 enters an operating state.

On the other hand, since the collector voltage of the transistor Q6 of the U / V switching circuit 4 becomes low level, VHF
The base voltage of the transistor Q3 in the oscillation circuit 2 drops, and the constant current source including the transistor Q3 and the resistors R3 and R4 is turned off. Therefore, no current flows through transistors Q1 and Q2, and VHF oscillation circuit 2 is in a non-operating state. That is, when the switch 5 in the VHF oscillation circuit 2 is connected to the UHF selection terminal 5b, the UHF oscillation circuit 3 is activated and the VHF oscillation circuit 2 is not activated.

Next, when the switch 5 in the VHF oscillation circuit 2 is connected to the VHF selection terminal 5a, the collector voltage and the base voltage of the transistor Q4 become the _Vcc voltage. As a result, the collector voltage of the transistor Q5 of the U / V switching circuit 4 becomes low level, so that the base voltages of the transistors Q9 and Q10 in the UHF oscillation circuit 3 drop, and the transistors Q9 and Q10 and the resistors R14 to
The constant current source composed of R16 turns off. Therefore, no current flows through transistors Q7 and Q8, and UHF oscillation circuit 3 enters a non-operating state.

On the other hand, since the collector voltage of the transistor Q6 of the U / V switching circuit 4 goes high, VHF
The base voltage of the transistor Q3 in the oscillation circuit 2 increases, and the constant current source including the transistor Q3 and the resistors R3 and R4 is turned on. Now, a base bias voltage is applied to each base of the transistors Q1 and Q2 from the constant voltage source VA via the resistors R1 and R2, and a power supply V is applied to the collector of the transistor Q1.
V _cc voltage is applied via the power supply terminal 6 _cc, to the collector of the transistor Q2, the transistor Q from the power supply V _cc is connected a choke coil L1 and the diode
Since V _cc voltage is applied via the 4, VHF oscillator circuit 2, becomes operational.

That is, when the switch 5 in the VHF oscillation circuit 2 is connected to the VHF selection terminal 5a, the UHF oscillation circuit 3 becomes inactive and the VHF oscillation circuit 2 becomes active. As described above, by switching the switch 5 in the VHF oscillation circuit 2, the VHF oscillation circuit 2 and the UHF
The HF oscillation circuit 3 can be controlled to operate / non-operate.

FIG. 4 shows a high-frequency integrated circuit 1 corresponding to the transistors Q2 and Q4 of the VHF oscillation circuit 2 shown in FIG.
FIG. 4, parts corresponding to those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 4, Q11 is a parasitic transistor and Q12 is a latch-up transistor.
Reference numerals 11 and Q12 denote unnecessary transistors that are inevitably formed in the process of configuring the high-frequency integrated circuit 1. R _s is the resistance of the substrate P ⁻ . In FIG. 4, the resistor R5 is shown outside the high frequency integrated circuit 1, but this is shown for convenience, and is actually configured inside the high frequency integrated circuit 1.

Here, the reason why the transistor Q4 and the resistor R5 are provided will be described. First, the transistor Q4 sets the switch 5 in the VHF oscillation circuit 2 to UHF
It is provided to prevent the collector voltage of the transistor Q2 from dropping when connected to the selection terminal 5b, that is, during UHF reception, to prevent the parasitic transistor Q11 from turning on.

Next, assuming that the resistor R5 is not provided, when the UHF is received, that is, when the switch 5 in the VHF oscillation circuit 2 is connected to the UHF selection terminal 5b, the collector of the transistor Q2 is in a floating state. become. At this time, despite the provision of the transistor Q4, if the collector voltage of the transistor Q2 becomes lower than the base voltage due to some cause, for example, power-on, the parasitic transistor Q11 is turned on, and the parasitic transistor Q11 is turned off by the collector of the transistor Q2. Transistor Q11
And the substrate P ^- collector current of (resistance component R _S) parasitic transistor Q11 to ground contacts 9 through may flow.

[0016] Accordingly, the substrate P ^- by the collector current of the resistance component R _S and the parasitic transistors Q11, the base voltage is increased latch-up transistor Q12, the latch-up transistor Q12 is turned on. This is a latch-up phenomenon. In order to prevent the latch-up phenomenon described above, the resistor R5 is a high resistance inserted between the power supply _Vcc and the collector of the transistor Q2 so that the collector voltage of the transistor Q2 does not drop below the base voltage.

[0017]

By the way, in the above-described conventional high-frequency integrated circuit 1, when receiving UHF, that is, when the switch 5 in the VHF oscillation circuit 2 is connected to the UHF selection terminal 5b, the collector voltage of the transistor Q4 is reduced. And the base voltage becomes 0 V, and the _Vcc voltage is applied to the emitter via the resistor R5. That is, the PN junction between the base and the emitter of the transistor Q4 is reverse-biased.

In general, the breakdown voltage of the PN junction of a high-frequency integrated circuit is low, that is, 2 to 3 V. Therefore, if the _Vcc voltage is higher than the breakdown voltage,
The diode-connected transistor Q4 is easily damaged. The present invention has been made under such a background, and to provide a high-frequency integrated circuit that is not damaged even when switching between a VHF oscillation circuit and a UHF oscillation circuit and that does not cause a latch-up phenomenon. With the goal.

[0019]

According to the present invention, in a high frequency integrated circuit having a VHF oscillation circuit and a UHF oscillation circuit and using either of them in an operation state, the VHF oscillation circuit has a collector connected to a power supply voltage. Is applied to the first transistor, the first transistor and the emitter are connected to each other, the collector is grounded during the operation of the UHF oscillation circuit, and the second transistor is applied with the power supply voltage during the operation of the VHF oscillation circuit. A first and second transistors, one end of which is connected to the base of each of the first and second transistors and the other end of which is connected to each other;
A constant current source interposed between the emitters of the first and second transistors and ground;
A third resistor interposed between a connection point between the first resistor and the second resistor and a collector of the second transistor; and a connection point between the first resistor and the second resistor. A fourth resistor interposed between the ground and a ground, and a fifth resistor interposed between the emitters of the first and second transistors and the ground and having a value that does not affect a high-frequency signal. It is characterized by having.

[0020]

According to the above configuration, during operation of the UHF oscillation circuit, the collector of the second transistor is grounded, but the emitters of the first and second transistors are
Grounded via the fifth resistor, the emitter voltage of each of the first and second transistors is approximately 0V. Further, the base voltage of each of the first and second transistors also becomes 0V.

[0021]

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a circuit diagram showing the configuration of a high-frequency integrated circuit 10 and its peripheral circuits according to an embodiment of the present invention. In this figure, the same reference numerals are given to parts corresponding to the respective parts in FIG. Omitted. In the high-frequency integrated circuit 10 shown in FIG.
Is removed, and the connection point between the choke coil L1 and the capacitor C3 is directly connected to the collector of the transistor Q2. Further, the constant voltage source VA and the resistor R5 are removed, and instead, a resistor R20 is interposed between the connection point between the resistors R1 and R2 and the collector of the transistor Q2, and the connection point between the resistors R1 and R2 is connected to the ground. And a resistor R21 is interposed therebetween. Further, a resistor R19 is newly provided between the transistor Q3 and the ground.

In such a configuration, when the switch 5 in the VHF oscillation circuit 2 is connected to the UHF selection terminal 5b,
The collector voltage of the transistor Q2 becomes 0V. As a result, the collector voltage of the transistor Q5 of the U / V switching circuit 4 goes high, so that the base voltages of the transistors Q9 and Q10 in the UHF oscillation circuit 3 rise,
Transistors Q9 and Q10 and resistors R14 to R1
6 is turned on. Now, the base of each of the transistors Q7 and Q8 has a constant voltage source V
A base bias voltage is applied from C via resistors R12 and R13, respectively, and transistors Q7 and Q8
Since the _Vcc voltage is applied from the power supply _Vcc to the respective collectors via the power supply terminal 6, the UHF oscillation circuit 3 is in the operating state.

On the other hand, since the collector voltage of the transistor Q6 of the U / V switching circuit 4 becomes low level, VHF
The base voltage of the transistor Q3 in the oscillation circuit 2 drops, and the transistor Q3 and the resistors R3, R4 and R1
9 is turned off. Therefore, since no current flows through transistors Q1 and Q2, V
The HF oscillation circuit 2 enters a non-operating state. That is, VH
When the switch 5 in the F oscillation circuit 2 is connected to the UHF selection terminal 5b, the UHF oscillation circuit 3 is activated and the VHF
The oscillating circuit 2 becomes inactive.

Next, when the switch 5 in the VHF oscillation circuit 2 is connected to the VHF selection terminal 5a, the collector voltage of the transistor Q2 becomes the _Vcc voltage. Thereby, U / V
The base voltage of the transistor Q5 of the switching circuit 4 goes high, turning on the transistor Q5. Therefore,
Since the collector voltage of the transistor Q5 goes low, the transistors Q9 and Q1 in the UHF oscillation circuit 3
0, the transistors Q9 and Q1
The constant current source composed of 0 and the resistors R14 to R16 is turned off. Therefore, no current flows through transistors Q7 and Q8, and UHF oscillation circuit 3 enters a non-operating state.

On the other hand, since the collector voltage of the transistor Q6 of the U / V switching circuit 4 becomes high level, VHF
The base voltage of the transistor Q3 in the oscillation circuit 2 rises, and the transistor Q3 and the resistors R3, R4 and R1
9 is turned on. Now, the base of each of the transistors Q1 and Q2 has a constant voltage source V
_cc to choke coil L1, resistors R20, R21, R1
And each base bias voltage via the R2 is applied to the collector of the transistor Q1, V _cc voltage is applied via the power supply terminal 6 from the power source V _cc, the collector of the transistor Q2, the choke from the power supply V _cc Since the _Vcc voltage is applied via the coil L1, the VHF oscillation circuit 2 is in the operating state.

That is, when the switch 5 in the VHF oscillation circuit 2 is connected to the UHF selection terminal 5a, the UHF oscillation circuit 3 is turned off and the VHF oscillation circuit 2 is turned on. As described above, by switching the switch 5 in the VHF oscillation circuit 2, the VHF oscillation circuit 2 and the UHF
The HF oscillation circuit 3 can be controlled to operate / non-operate.

Here, the reason why the resistor R19 is provided will be described. Assuming that the resistor R19 is not provided, when receiving UHF, that is, when the switch 5 in the VHF oscillation circuit 2 is connected to the UHF selection terminal 5b, the emitters of the transistors Q1 and Q2 and the collector of the transistor Q3 are In a floating state, that is, a state in which the power supply and the ground are separated by high impedance, the respective emitter voltages of the transistors Q1 and Q2 and the collector voltage of the transistor Q3 become
A specific voltage value between the power supply voltage and the ground (hereinafter, referred to as a floating voltage).

On the other hand, since the base voltages of the transistors Q1 and Q2 are 0 V, the PN junction between the base and the emitter of the transistors Q1 and Q2 is reverse-biased by the above-mentioned floating voltage. When this floating voltage exceeds 2-3V, the transistor Q1
And the base-emitter of Q2 may break down and be damaged. To prevent this,
The resistor R19 has such a high resistance that does not affect the high-frequency signal inserted between the collector of the transistor Q3 and the ground in order to reduce the floating voltage to almost 0V.

Next, FIG. 2 shows a partial structural cross-sectional view of the high-frequency integrated circuit 1 corresponding to the transistors Q1 to Q3 of the VHF oscillation circuit 2 of FIG. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 2, Q13~Q15 parasitic transistor, R _s is the substrate P ^- is the resistance of. In FIG. 2, the resistance R
1 to 4 and R19 to R21 are illustrated outside the high-frequency integrated circuit 1, but are illustrated for convenience.
Actually, it is configured in the high-frequency integrated circuit 1.

The high-frequency integrated circuit 10 according to one embodiment of the present invention also has a latch-up transistor as in the prior art, but is not shown in FIG. The latch-up phenomenon does not occur in the high-frequency integrated circuit 10 according to one embodiment of the present invention for the following reason. At the time of UHF reception, that is, when the switch 5 in the VHF oscillation circuit 2 is connected to the UHF selection terminal 5b, the respective base voltages of the transistors Q1 and Q2 are:
0V, and the base voltage of the transistor Q3 is almost 0V (strictly speaking, the collector-emitter saturation voltage of the transistor Q6) because the transistor Q6 is in the ON state. Therefore, parasitic transistors Q13-Q
Since the transistor 15 is not turned on, a latch-up transistor (not shown) is not turned on, and no latch-up phenomenon occurs.

As described above, according to one embodiment of the present invention, the damage of the transistor Q4, which has conventionally occurred at the time of UHF reception, is such that the transistor Q4 is removed.
Does not occur. Further, since the parasitic transistors Q13 to Q15 and the latch-up transistors, which are unnecessary transistors inevitably formed in the process of configuring the high-frequency integrated circuit, do not turn on, the latch-up phenomenon does not occur.

[0032]

As described above, according to the present invention, there is an effect that even if the VHF oscillation circuit and the UHF oscillation circuit are switched, they are not damaged by latch-up or transistor breakdown. In addition, since it is not necessary to consider the breakdown voltage, there is an effect that the setting range of the power supply voltage is wide.

[Brief description of the drawings]

FIG. 1 is a high-frequency integrated circuit according to an embodiment of the present invention;
FIG. 2 is a circuit diagram showing a configuration of a peripheral circuit.

FIG. 2 is a partial structural cross-sectional view of the high-frequency integrated circuit 10 of FIG.

FIG. 3 is a circuit diagram showing a configuration example of a conventional high-frequency integrated circuit 1 and its peripheral circuits.

4 is a partial cross-sectional view of the high-frequency integrated circuit 1 of FIG.

[Explanation of symbols]

1,10 high frequency integrated circuit 2 VHF oscillator circuit 3 UHF oscillation circuit 4 U / V switching circuit 5 switches 5a VHF selection terminal 5b UHF selection terminal Q ₁ to Q ₁₀ transistor R ₁ to R ₂₁ resistors

Claims (1)

(57) [Scope of request for utility model registration] 1. A high-frequency integrated circuit that has a VHF oscillation circuit and a UHF oscillation circuit and uses one of them in an operating state, wherein the VHF oscillation circuit has a collector to which a power supply voltage is applied. A second transistor, wherein the first transistor and the emitter are connected to each other, the collector of which is grounded during the operation of the UHF oscillation circuit, and the power supply voltage is applied during the operation of the VHF oscillation circuit.
And a first and second resistor having one end connected to the base of each of the first and second transistors, and the other end connected to each other, and the emitter of the first and second transistors. A constant current source interposed between the first resistor and the ground; a connection point between the first resistor and the second resistor;
A third resistor interposed between the collector of the transistor and a fourth resistor interposed between a connection point between the first resistor and the second resistor and a ground; A high-frequency integrated circuit, comprising: a fifth resistor interposed between the emitters of the first and second transistors and ground and having a value that does not affect a high-frequency signal.