JPS60144023A - Oscillating circuit - Google Patents

Abstract

PURPOSE:To constitute so that an oscillation level is not varied by a frequency when an oscillation frequency range is wide, by switching current quantity of a current source of an oscillating circuit in accordance with an oscillation frequency. CONSTITUTION:Controlling of current quantity of a transistor (Tr)39 which becomes an operating current source of an oscillating circuit 30 is executed by control of a bias voltage from a base bias circuit 60 of the Tr39. That is to say, when a changeover switch 70 is connected to a terminal 70a side, a voltage VA1 of a connecting point A is determined by a +B power supply voltage and a voltage drop of a series of diodes and a resistance 66, in accordance with which an output voltage VB1 of the circuit 60 is determined. When the switch 70 is switched and connected to a terminal 70b side, a voltage VA2 of the connecting point A becomes higher than the voltage VA1, in accordance with which a base bias voltage VB2 also becomes higher than the voltage VB1, and a current quantities from the Trs 39, 57 become more than the previous case. Accordingly, for instance, when a local oscillation frequency becomes high, the current quantity of the operating current source 30 increases by switching the switch 70 to the terminal 70b.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an oscillation circuit capable of widening the oscillation frequency range, and particularly to a wideband television circuit capable of receiving not only Vl (F signals) but also CATV signals. Station rXl
(Relating to an oscillation circuit suitable for use in an oscillation circuit.

[Spine technology and its problems]

It is generally known that in oscillation circuits with a wide oscillation frequency range, the oscillation level varies depending on the frequency, and for this reason, when used in local oscillators such as chisels,
The drawback was that tracking was difficult.

In particular, when one tuner circuit configuration is capable of receiving not only VHF broadcast signals but also CA'TV broadcast signals, the reception frequency band is from several tens of MHz2η1 to several hundred MHz.
Since the range is extremely wide, if the oscillation output level in the middle and low ranges within this range is taken as the standard, the level drop in the high range side will be significant.

Therefore, it is conceivable to use multiple oscillation circuits by switching them according to the oscillation frequency band, but when converting to an IC (integrated circuit), the number of bins will increase, and the IC scale will be large. Furthermore, since a resonant circuit is also required for each oscillation circuit, the number of parts increases.

[Purpose of the invention]

In view of the above-mentioned circumstances, the present invention solves the problem that the oscillation level fluctuates greatly depending on the frequency when the oscillation frequency range is wide by switching the current amount of the current source of the oscillation circuit according to the oscillation frequency. At the same time, it is easy to convert to 1C (
The purpose of the present invention is to provide an oscillation circuit that is suitable for integrated circuits (integrated circuits) and is capable of stably oscillating over a wide frequency range.

[Overview of the invention]

In other words, the oscillation circuit according to the present invention is characterized in that, in an oscillation circuit whose oscillation level changes depending on the current and oscillation frequency of the current source of the oscillation circuit, the amount of current of the current source is adjusted to the oscillation frequency. The oscillation level is kept approximately constant by controlling the oscillation level by switching, for example, depending on the oscillation level. Therefore, compared to the case where the current is fixed, the maximum oscillation frequency can be set higher, and it is possible to solve the problem that the excavation level fluctuates greatly depending on the frequency. It has the advantage that the configuration is simple and the number of external connections 1v11.1 when integrated into an IC can be reduced.

〔Example〕

First, prior to a detailed explanation of the present invention, we will first explain an example of a no-revision business using an oscillation circuit according to the present invention as a local oscillation circuit. Please refer to figure 11'! (jL will explain.

In this FIG. 1, ICC integrated circuit for tuner) 10
The input terminal 1 of the
Several dozen M11z to several white MH20RF signals of ATV signal q. are supplied. This input RF signal is the tuner I
The signal is sent to a mixer (so-called mixer) 3 via a buffer amplifier 2 in Cl0, where it is mixed with the oscillation output from a local excavation circuit 4 consisting of an oscillation circuit of the present invention, which will be described later, and converted into an intermediate frequency signal (so-called IFF signal). The IF (W) from the mixer 3 is taken out from the output terminal 7 via the IF amplifier 5 and the IF output circuit 6.
During HF reception, a so-called UIF signal, which is a UHF signal from the UI (F tuner section, etc.) converted into an intermediate frequency signal, is supplied to the input terminal 8, and this UIF signal is sent to the UIF amplifier 9.
A UIF signal is output from the mixer 3 by not sending it to, for example, a load resistor in the mixer 3 through the IF.
Output terminal 7 via amplifier 5 and IF output circuit 6)
IVi,') is issued.

Next, in the local oscillation circuit 4 in the tuner ICl0,
A resonant circuit (so-called tank circuit) 14 having a coil, a capacitor, etc. is connected through nine CIA connections 11, 12, and 13. The oscillation output of the local excavation circuit 4 A part of the so-called PLL circuit is I'
It is output from a terminal 16 via a buffer amplifier 15 as a pickup output for forming f'7. This pink amplifier output is sent to the programmable divider 18 via the prescaler 11. Prescaler 17 is
The programmable divider 18 divides the pickup output by i't'+1 to a frequency that can be divided by i't'+1, and the frequency division ratio is fixed, whereas the programmable divider 18 can select a station. The frequency division ratio changes depending on the signal.

The output from the programmable divider 18 is sent to a phase comparator 19 where it is compared with a constant frequency reference signal. The phase-compared output is sent to the channel selection control voltage generation circuit 21 via an LPF (low-pass filter) 20, and the output voltage is sent to a variable displacement element of the resonant circuit 14, for example, a vari-gap diode. , local excavation frequency control is performed.

In addition, the terminal 22.2 led out from the mixer 3 to the outside of the IC
3, an IC resonant circuit 24 may be connected as necessary, and the mixer 3 may be provided with the above-mentioned IF (of the bandpass m that outputs only the i-th frequency component;'F241<IVi property. .

With this type of configuration, a so-called frequency synthesizer type television VHF tuner, 6 is a normal VHF tuner.
'Receive not only broadcast signals but also CATV broadcast signals11'
In the case of a capable tuner, the reception (,-i frequency is several tens of M
Hz to several hundred MHz (for example, 54MHz in the United States)
z to 470 MHz), the oscillation output level of the local oscillation circuit generally varies depending on the frequency, making tracking difficult.

Therefore, the oscillation circuit according to the present invention maintains the oscillation output level substantially constant by controlling the current of the current source for oscillation according to the oscillation frequency.

＼ That is, FIG. 2 shows the above-mentioned first embodiment as an embodiment of the present invention.
An oscillation circuit suitable for use in the local oscillation circuit 4 shown in the figure is shown.

In the embodiment of the present invention shown in FIG.
A so-called differential oscillation circuit is configured using a MID amplifier of type transistors 31 and 32. Each base of these pair of transistors 31, 320 has a voltage dividing resistor 33,
34, a transistor 35, and a resistor 36 serving as a constant current source. A DC voltage is supplied from a base bias voltage source circuit through resistors 37 and 38, respectively. A transistor 39 serving as a constant current source and a series circuit of a resistor are connected to the commonly connected emitters of the transistors 31 and 32, and the base and collector of the transistor 31 and the base of the transistor 32 are connected to terminals 11, 12, and 13, respectively.
It is connected to a resonant circuit (so-called tank circuit) 14 via a. Here, the main parts of the oscillator other than the resonant circuit 14 are configured, for example, inside a tuner IC (integrated circuit), and each of the terminals 11, 12, and 13 corresponds to an external connection bin of the IC. .

The resonant circuit 14 connects the terminal 1 to the collector of the transistor 61.
The main part is a parallel resonant circuit consisting of a capacitor 45 and a coil 46 connected through terminal 1.
2.13 are connected through a capacitor 47, and the resonant frequency component approximately determined by the parallel resonant circuit of the collector output of one transistor 61 of the transistor differential pair is positively connected to the base of the other transistor 62. Oscillating operation is performed by returning to the ring. -! ,Ta,
A capacitor 48 is connected to the terminal 11 led out from the base of the transistor 610.Furthermore, since it is used as the local oscillation circuit 4 of the television cheese shown in FIG. Therefore, a series circuit of a capacitor 49 and a varicap diode 50 is connected in parallel to the capacitor 45 of the parallel resonant circuit, and a series circuit of a capacitor 49 and a varicap diode 50 is selected. A control voltage for station tuning is applied via a terminal 51 and a resistor 52.

−The main oscillating output from such an oscillator circuit is then:
The signal is taken out through a pair of transistors 55 and 56 whose emitters are commonly connected, which serve as a buffer. In other words, the bases of the transistors 55, 56 constituting the common emitter transistor pair are connected to the bases of the transistors 31, 32, which serve as differential amplifiers for oscillation. A transistor 57 serving as a constant current source is connected to the commonly connected emitters of
and a series circuit of resistors are connected. The output current from each collector of these transistors 55 and 56 is sent via a buffer amplifier 58 to the mixer 3 of the television tuner described above. Note that the pink-up output to the PLL system is not shown, but for example, from a part of the buffer amplifier 5B or -17A/j+ of the transistor 32, p coffee IL
^46h Doshishi, just take it out.

Next, as the gist of the present invention, a configuration will be described in which the amount of current of the transistor 39 serving as the operating current source of the oscillation circuit is controlled according to the oscillation frequency. This can basically be done by controlling, for example, switching the bias voltage from the transistor 390 base bias circuit 60 serving as the current source. That is, in FIG. 2, a bias voltage from a base bias circuit 60 is supplied to the bases of transistors 39 and 9, which serve as constant current sources of each differential amplifier. This base bias circuit 60 connects an NPN transistor to each base of each NPN transistor 39°57 serving as the current source.
The main parts of the transistor 610 are connected to the base of a type transistor 610, the base of an NPN type transistor 62 is connected to the collector of this transistor 61, and the emitter of this transistor 62 is connected to the base of the transistor 610. Note that the emitter of the transistor 62 is connected to the resistor 63 through the resistor 63, and the emitter of the transistor 61 is connected to the resistor GA through the resistor 63. A series circuit of a plurality of diodes 65a, 65b, .
and diodes 65a, 65b,"
The emitter collector of 1.PNP type transistor 6γ is connected in parallel to the series circuit of y65n, and the voltage dividing resistor 68,6 is connected to the base of this transistor 67.
9 is connected to the common terminal γOc of the changeover switch 70. One switching selection terminal 70a of this changeover switch 70 is in an open state, and the other terminal 70a is in an open state.
b is grounded.

With this fl, 4':1'J configuration υ, the voltage VA appearing at the connection point between the collector of the transistor 61 and the base of the transistor 620, and each constant current source transistor 39 which becomes the output terminal of the base bias circuit 60. .510 Base bias voltage VB appearing at connection point BK with each base
This will be explained together with the switching operation of the changeover switch 70. First, set the selector switch 70 to the terminal? When switched to the Oa side, the PNP type transistor 67 is turned off, and the collector of the transistor 61 and the transistor 62 are connected.
The voltage VA1 to the connection point with the 0 base is →-■ 3 lines'
From the tonnage pressure, diodes 65a, 65b,..., 65n
The output voltage V of the base bias output circuit 60 is determined accordingly. Next, when the changeover switch 10 is connected to the terminal 10b side,
1) The NL) type transistor 6T is almost in the on state (saturated state), and the diodes 65a, 65by"・p65n
The threshold voltage across the terminals of the series circuit of is equal to the emitter-collector voltage VCE of the transistor 67, which is 1. Since the voltage drop of the diode series circuit is also smaller, the voltage VA2 to the connection point at this time is higher than the voltage vA19. Accordingly, the base bias voltage v112 and the voltage vB2 are also the voltage VB, appears higher than.

Therefore, the amount of current in each constant current source made up of the transistors 39 and 57 decreases when the switching switch 110 is switched connected to the terminal 70a, and increases when switched connected to the terminal 70b. Therefore, the analogy is to keep in mind the tuner.
When the frequency is high<)L"JWlj the oscillation frequency is still low, by switching and connecting the changeover switch γat to the terminal 70b, the amount of current of the operating current source of the oscillation circuit upper part 30 increases, and the oscillation level decreases. In order to prevent this, it becomes possible to obtain a substantially constant oscillation level over a wide frequency band.Specifically, the above-mentioned Vl-f1'' (6
When using the oscillation circuit of the embodiment of FIG. 2 in the local oscillation circuit 4 of the television tuner of FIG.
When receiving a 0MHz VHF signal, switch:, /
P2O to terminal 70al1llIK4JJJ'i! 3Jg
MJt, When receiving CATV signals of approximately 200MHz to several hundred MHz, connect the selector switch 10 to the terminal 70bill.
! It is only necessary to switch the connection to 1, and such switching may be performed in conjunction with, for example, a channel selection operation.

Note that a voltage source for bringing the transistor 67 into a substantially saturated state is connected to the terminal 70b of the changeover switch 70. temotoyoku, sunx end-"i'7n, I soup cow R lightning suppository 4&%a
You may. Furthermore, it goes without saying that the U-month fault switch 70 may be configured as a so-called ``11L IJJ exchange switch'' using a semiconductor element configuration.

According to the embodiment of the present invention having the above-described configuration, by configuring the oscillation circuit main section 30 using the amplifier fully differential transistor pair and the constant current source, It becomes possible to control the output (1) and suppress level fluctuations when the Q frequency changes.
In the past, when the oscillation circuit was configured with 40 discrete units, there was only one oscillation transistor.
This is because the use of an IC has made it possible to easily use a differential amplifier configuration. Furthermore, compared to a system in which a compound oscillation circuit and a resonant circuit are switched, the resonant circuit configuration is simpler and the number of externally connected pins is smaller, making the circuit configuration suitable for IC implementation.

Note that the present invention is not limited to the above-mentioned embodiments; for example, the current control of the operating current source of the differential amplifier in the main part of the boosting circuit may be configured in various ways, and the base bias voltage may be adjusted in three or more stages. The bias voltage may be changed continuously by 1'' in an analog manner. In addition to local oscillation circuits for television tuners, the present invention can of course be applied to oscillation circuits with a relatively wide oscillation frequency range.

〔Effect of the invention〕

The oscillation circuit according to the VC of the present invention can suppress fluctuations in the oscillation level when the oscillation frequency changes over a wide frequency range. In addition, when considering IC implementation, the number of parts and external terminal bins are small compared to a system that switches between multiple systems of oscillation circuits, making it suitable for IC implementation.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing an example of a television tuner circuit to which a broadband excavation circuit according to the present invention is applied, and FIG. 2 is a circuit diagram showing one implementation of the present invention. 14...Resonance circuit 30...Oscillation circuit main part 31.32...NPN type transistor 39.57...
・Transistor 60 serving as a constant current source...Base bias circuit 70...Switch switch Patent applicant Sony Corporation Patent attorney Miumi Koike 1) Sakae Mura -

Claims (1)

[Claims] In a variable frequency oscillation circuit in which the oscillation output level depends on the oscillation frequency and depends on the current of the operating current source of the oscillation circuit, the oscillation level can be adjusted by controlling the current of the current source according to the oscillation frequency. A J/C circuit that is characterized by keeping the output constant.