JPH10335933A - Oscillator circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To save space, also to reduce cost and to prevent the oscillation of a frequency that is different from a prescribed frequency by providing a means, which prevents the oscillation of a frequency that is different from a prescribed frequency in an oscillator circuit which consists of an integrated circuit that integrates plural elements and an external circuit and oscillates in a prescribed frequency. SOLUTION: An oscillator circuit 1 is provided with an exterior circuit part 10, which is externally attached to an IC part 20 and forms a feedback circuit and the part 20 that forms an amplifier circuit which consists of plural integrated elements. The part 20 is provided with a resistance R1, whose one end is connected to the other end of a capacitor C3 via an external terminal 22 and an amplifier AMP 1, where the other end of the resistance R1 is connected to an input terminal side. Furthermore, the other end of a capacitor C2 is connected to an output terminal side via an external terminal 21. Because the resistance R1 is provided and the resistance R1 and a capacitor C4 constitute a low-pass filter, gain in high region becomes low and parasitic oscillations at high frequencies does not take place due to a parasitic element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an oscillation circuit that oscillates at a predetermined frequency.

[0002]

2. Description of the Related Art For example, a TV (television) tuner or the like is provided with an oscillation circuit formed by using an IC (integrated circuit) chip. The oscillation circuit includes an IC in which a plurality of elements are integrated, and an external circuit external to the IC. The oscillation circuit amplifies an input signal by an amplification circuit and outputs the amplified signal. The oscillation at a predetermined frequency is performed by returning a part of the output to the input of the amplifier circuit by a feedback circuit.

FIG. 4 is a circuit diagram showing an example of a conventional oscillation circuit used in a TV tuner or the like. As shown in FIG. 4, a conventional oscillation circuit includes an external circuit section 100 externally formed to an IC section 200 described later to form a feedback circuit, and an IC section formed by integrating a plurality of elements to form an amplifier circuit. 200. In the figure, only the main circuit portion of the oscillation circuit is shown, and for example, a power supply circuit portion for supplying power is omitted.

The external circuit section 100 has an inductance L110 having one end grounded, and a capacitor C1 having one end grounded and the other end connected to the other end of the inductance L110.
10, one end having an inductance L110 and a capacitance C1.
10 and a capacitor C1 whose other end is connected to the external terminals 210 and 220 of the IC unit 200, respectively.
20 and a capacitor C130.

The IC section 200 has an external terminal 2 on the input terminal side.
An amplifier AMP10 is connected to the other end of the capacitor C130 via an external terminal 20 and connected to the other end of the capacitor C120 via an external terminal 210 on the output terminal side.

When a power supply (not shown) is turned on in the oscillation circuit having such a configuration, first, noise is generated in the IC section 200, and this noise is transmitted through the external circuit section 100 forming a feedback circuit. The signal is fed back to the input of the amplifier AMP10. The noise generated when the power is turned on is broadband noise, but only the same frequency component as the resonance frequency in the resonance circuit including the inductance L110 and the capacitor C110 has a gain and is fed back to the input of the amplifier AMP10. Such feedback and amplification are repeated, and the output level of the above-mentioned resonance frequency gradually increases, and oscillation at the resonance frequency, that is, a desired predetermined frequency occurs.

In the oscillation circuit having the above configuration, the predetermined oscillation frequency is determined by the resonance frequency of the external inductance L110 and the capacitance C110. In the conventional oscillation circuit, the predetermined oscillation frequency is determined by the resonance frequency. Oscillation may occur at a frequency different from a predetermined oscillation frequency called parasitic oscillation instead of the frequency.

[0008] Such parasitic oscillation is caused by the influence of a so-called parasitic element in the oscillation circuit. The parasitic element is mainly formed in the IC unit 200. For example, as a parasitic inductance which is one of the parasitic elements of the IC unit 200, a wiring inductance in an IC chip, a bonding wire, an inductance of a lead frame, and the like. There is. The parasitic capacitance is the capacitance of a pad (Pad), which is a portion from which a bonding wire is drawn.
There is a capacitance between pins of the lead frame.

FIG. 5 is a circuit diagram showing an example of an oscillation circuit taking into account the parasitic element formed in the IC section 200 as described above. In this oscillation circuit, in addition to the configuration of the circuit shown in FIG.
10, an inductance L210 connected to the output side of
An inductance L220 having one end connected to the input side of the amplifier AMP10, and an inductance L230 having one end connected to the other end of the capacitor C120 via the external terminal 210 and the other end connected to the other end of the inductance L210.
And an inductance L240 having one end connected to the other end of the capacitor C130 via the external terminal 220 and the other end connected to the other end of the inductance L220, and one end connected between the inductance L210 and the inductance L230. Are capacitors C210 and C22 connected between the inductance L220 and the inductance L240.
0.

In this circuit, for example, the inductance L210 is the wiring inductance in the IC chip,
The inductance L230 is an inductance of a bonding wire or a lead frame. In addition, the capacity C21
0 is the capacitance of the pad, and the capacitance C220 is the capacitance between the pins of the lead frame.

As described above, the values of the inductance and the capacitance due to the parasitic element formed in the IC unit 200 are smaller than the values of the external inductance L110 and the capacitance C110 constituting the resonance circuit, and the resonance frequency is higher than the desired frequency. Depending on the conditions, oscillation may occur at a high frequency determined by these parasitic elements.

Conventionally, in order to prevent the parasitic oscillation caused by the parasitic element, a low resistance of several tens of Ω for preventing the parasitic oscillation is inserted into the external circuit section 100 forming the feedback circuit, and the gain in the high band ( By lowering the gain, parasitic oscillation that oscillates at a high frequency is suppressed.

FIG. 6 is a circuit diagram showing an example of a conventional oscillation circuit provided with such a resistor for preventing parasitic oscillation. In this circuit, in addition to the configuration of the circuit shown in FIG. 4, a low resistance R110 for preventing parasitic oscillation is externally provided between the capacitor C130 and the input side of the amplifier AMP10.

[0014]

However, the structure of the above-described conventional oscillation circuit has a problem that an external space for providing a resistor for preventing parasitic oscillation is required, and the number of external components is reduced. Therefore, there is a problem that the production cost is increased due to an increase in the number of components.

The present invention has been made in view of the above problems, and has as its object to provide an oscillation circuit capable of preventing oscillation at a frequency different from a predetermined frequency in a small space at a low cost. It is in.

[0016]

An oscillation circuit according to the present invention is provided with oscillation prevention means for preventing oscillation at a frequency different from a predetermined frequency in an integrated circuit.

In the oscillation circuit according to the present invention, oscillation at a frequency different from a predetermined frequency such as a parasitic oscillation can be achieved by the oscillation preventing means provided in the integrated circuit without providing an external resistor as in the prior art. Is prevented.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] First, the first embodiment of the present invention will be described.
An embodiment will be described. FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a circuit diagram showing a configuration of an oscillation circuit according to the embodiment. Here, as an example of the oscillation circuit of the present invention, T
A local oscillator circuit formed into an IC used in a V tuner or the like will be described.

As shown in FIG. 1, an oscillation circuit 1 according to the present embodiment is formed by integrating an external circuit section 10 externally attached to an IC section 20 described later to form a feedback circuit, and a plurality of elements. And an IC section 20 which forms an amplifier circuit. In the figure, only the main circuit portion of the oscillation circuit is shown, and for example, a power supply circuit portion for supplying power is omitted.

The external circuit section 10 includes an inductance L1 having one end grounded, a capacitor C1 having one end grounded and the other end connected to the other end of the inductance L1, and one end having the inductance L1 and the capacitance C1. It is configured to include a capacitor C2 and a capacitor C3 connected to one end and the other end connected to the external terminals 21 and 22 of the IC unit 20, respectively.

In the external circuit section 10, the inductance L1 and the capacitance C1 constitute a resonance circuit and determine the oscillation frequency of the oscillation circuit 1. The capacitors C2 and C3 are feedback capacitors for applying a positive feedback to the amplifier AMP1.

The IC unit 20 includes a resistor R1 having one end connected to the other end of the capacitor C3 via the external terminal 22, a resistor R1 connected to the input terminal, and an external terminal 21 connected to the output terminal. A to which the other end of the capacitor C2 is connected via
MP1. In addition, an input capacitance C4 that appears on the base side of a transistor (not shown) exists between the input side of the amplifier AMP1 and the other end of the resistor R1 and the ground. Note that the resistor R1 is a resistor for preventing parasitic oscillation, and corresponds to the oscillation preventing means of the present invention.

When a power supply (not shown) is turned on in the oscillation circuit having such a configuration, first, noise is generated in the IC section 20, and this noise is transmitted through the external circuit section 10 forming a feedback circuit. The signal is fed back to the input of the amplifier AMP1. The noise that occurs when the power is turned on is broadband noise,
Only the frequency component equal to the resonance frequency in the resonance circuit including the inductance L1 and the capacitance C1 has a gain and is fed back to the input of the amplifier AMP1. Such feedback and amplification are repeated, and the output level of the resonance frequency gradually increases, and the resonance frequency, that is,
Oscillation occurs at the desired predetermined frequency.

Next, the operation of the resistor R1, which is a feature of the present invention, will be described. For example, if the resistor R1 is not provided in the oscillation circuit 1, the feedback amount is fed back to the input of the amplifier AMP1 at a level divided by the impedance of the capacitors C3 and C4. However, the resistance R1
Is provided, resistance L1 and capacitance C4 cause L
Because it constitutes a PF (low-pass filter),
The gain in the high range becomes lower. As a result, the feedback amount of the high-frequency parasitic oscillation becomes small and the oscillation condition is not reached, so that the high-frequency parasitic oscillation due to the parasitic element does not occur.

The value of the resistor R1 differs from several Ω to several tens of Ω depending on the conditions of the oscillation circuit 1, and an accurate value is not known until the IC section 20 is evaluated. For this reason, several resistive elements having a conceivable resistance value are prepared on the IC chip of the IC section 20 in advance, and if parasitic oscillation occurs,
According to the evaluation result of the part 20, it is preferable to connect each resistance element in series or in parallel by aluminum wiring, thereby producing a desired resistance value.

As described above, according to the oscillation circuit 1 of the present embodiment, the resistor R1 for preventing parasitic oscillation is connected to the IC
By providing it in the unit 20, since a conventional external resistor for preventing parasitic oscillation is not required, the number of components on a substrate on which circuit elements are mounted is reduced, and cost can be reduced. In addition, since there is no need for a space for an external resistor on the substrate, there is an effect that the degree of freedom in designing the substrate is increased. This makes it possible to prevent the oscillation at a frequency different from the predetermined frequency from being performed in a space-saving manner and at low cost.

[Second Embodiment] Next, a second embodiment of the present invention will be described.
An embodiment will be described. In the following description, the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the oscillation circuit 1 according to the first embodiment, when the value of the resistor R1 is as large as about several tens of ohms,
The purpose of preventing parasitic oscillation can be sufficiently achieved by preparing several resistive elements of a desired value on an IC chip in advance, but if the value of the resistor R1 is as small as several Ω, 1 It is difficult to realize the resistance R1 for preventing parasitic oscillation with one resistance element, and it is necessary to connect a plurality of resistance elements in parallel. In this case, problems such as an increase in the space occupied by the resistance elements and an influence on the oscillation characteristics due to the occurrence of parasitic capacitance due to the plurality of resistance elements are conceivable.

In the present embodiment, in order to eliminate such a problem, the formation of the resistor R1 requires a via hole (conduction hole) in the IC.
It is a thing using.

FIG. 2 is a configuration diagram of a via hole for describing an oscillation circuit according to a second embodiment of the present invention.

FIG. 2A shows a sectional structure of a via hole portion. As shown in this figure, the via hole portion VH is for making a conductive connection between the different wiring layers 31 and 32 to be laminated, and a via hole 30 a penetrating through the insulating layer 33 and a via hole 30 a inside the via hole 30 a are provided. And a buried conductor 30b.

Here, the conductor 3 in the via hole portion VH
Ob is made of, for example, aluminum or the like, and usually has a resistance value of about several hundred m [Ω]. For this reason, by connecting a plurality of via hole portions VH alternately in series between the wiring layers 31 and 32, it is possible to easily create a low resistance required for the resistor R1 for preventing parasitic oscillation.

FIG. 2B shows the structure of the via hole VH when the resistor R1 is formed using the via hole VH. In FIG. 2B, a plurality of via hole portions VH1 to VH5 are alternately connected in series between the wiring layers 31 and 32 to form a low resistance necessary for the resistor R1 for preventing parasitic oscillation. Since the resistor R1 formed by the plurality of via hole portions VH1 to VH5 can be realized with the same width as the wiring width of the aluminum wiring, it does not take up a large space unlike a normal resistance element.

FIG. 2B shows a case where five via hole portions VH1 to VH5 are used.
Via hole V used as resistor R1 for preventing parasitic oscillation
The number of H is not limited to five, and the number of via holes corresponding to the resistance value necessary for preventing the parasitic oscillation is used.

As described above, the oscillation circuit according to the present embodiment has the following effects in addition to the effects of the oscillation circuit 1 according to the first embodiment. First, by using the via hole portion VH, a low resistance for preventing parasitic oscillation can be realized in a small space corresponding to the width of the aluminum wiring, so that there is no need to consider a space for providing a resistance element. Further, since the resistance value formed in the via hole portion VH has a small variation, the circuit can be designed with high accuracy. Further, since the number of via hole portions VH can be increased by an arbitrary number by changing the process after the formation of the aluminum wiring, trimming (adjustment of resistance value) is easy.

The present invention is not limited to the above embodiments, and various modifications can be made. For example, in the above embodiment, the positive feedback oscillation circuit has been described.
The present invention is similarly applied to a Colpitts type oscillation circuit.

FIG. 3 is a circuit diagram showing an example of a Colpitts type oscillation circuit to which the oscillation circuit of the present invention is applied. In addition,
In the figure, only a main circuit portion of the oscillation circuit is shown, and for example, a power supply circuit portion for supplying power is omitted.

The Colpitts type oscillation circuit 1a shown in FIG.
The external circuit section 10a has an inductance L11 and a capacitor C11 connected in parallel to each other, one end connected to one end of the inductance L11 and the capacity C11, and the other end connected to an external terminal 23 of the IC section 20a. One end of the capacitor C12 is connected to the inductance L11 and the other end of the capacitor C11, and the other end is connected to the IC section 20a.
C13 connected to the external terminal 26 of the capacitor C1 and a capacitor C1 connected at one end to the other end of the capacitor C12 and the external terminal 23.
4, one end of the capacitor C15 connected to the other end of the capacitor C14 and the external terminal 24, and one end connected to the other end of the capacitor C15 and the external terminal 25, and the other end connected to the other end of the capacitor C13. And a capacitance C16.

One end of the capacitor C is used as the IC section 20a.
12, a resistor R11 connected to the other end of the capacitor C14 via the external terminal 23, a resistor R12 connected to the other end of the capacitor C13 and the capacitor C16 via the external terminal 26, and a resistor R12 connected to the base side. A transistor Q1 connected to the other end of R11 and having an emitter connected between the capacitors C14 and C15 via an external terminal 24; a base connected to the other end of the resistor R12 and an emitter connected to the external terminal 25;
And a transistor Q1 connected between the capacitor C15 and the capacitor C16 through the capacitor C15. The emitter and the collector of the transistor Q1 are connected to a current source, a power supply (not shown), and the like, respectively. The emitter and the collector of the transistor Q2 are also connected to a current source, a power supply (not shown), and the like.

In the Colpitts type oscillation circuit 1a having such a configuration, the resistor R11 provided in the IC section 20a is provided.
The resistor R12 is a resistor for preventing parasitic oscillation, and corresponds to the oscillation preventing means of the present invention. With the oscillation circuit 1a provided with such a resistor, the same effect as the oscillation circuit 1 of the above embodiment can be obtained.

[0042]

As described above, claims 1 and 4
According to the oscillation circuit described in any of the above, oscillation prevention means for preventing oscillation at a frequency different from the predetermined frequency is provided in the integrated circuit. Is unnecessary, the number of components on the substrate on which the circuit element is mounted is reduced, and the cost can be reduced. In addition, since there is no need for a space for an external resistor on the substrate, there is also an effect that the degree of freedom in designing the substrate is increased. This makes it possible to prevent the oscillation at a frequency different from the predetermined frequency from being performed in a space-saving manner and at low cost.

According to the oscillation circuit of the third or fourth aspect, a conductor formed in a conduction hole for connecting different wiring layers in the integrated circuit is used as the oscillation preventing means. Therefore, in addition to the effect of the oscillation circuit according to the first aspect, the oscillation preventing means can be realized in a small space of only the wiring width in the integrated circuit, and it is necessary to consider a space for providing a normal circuit element. There is an effect that there is no.
In addition, the variation in the characteristics is smaller than that of the oscillation preventing means formed by ordinary circuit elements, so that the circuit can be designed with high accuracy. Further, since the number of conductive holes can be increased by an arbitrary number by a change in the process after forming the normal wiring, trimming is easily performed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an oscillation circuit according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a main part of an oscillation circuit according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration of an oscillation circuit according to another embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a conventional oscillation circuit.

FIG. 5 is a circuit diagram showing a configuration of the oscillation circuit of FIG. 4 in consideration of a parasitic element.

FIG. 6 is a circuit diagram showing the configuration of another conventional oscillation circuit.

[Explanation of symbols]

10, 10a: external circuit section, 20, 20a: IC section, 3
0a: via hole, 30b: conductor, R1: resistance (oscillation prevention means), VH: via hole

Claims (4)

[Claims] An integrated circuit in which a plurality of elements are integrated, and an external circuit external to the integrated circuit,
An oscillation circuit which oscillates at a predetermined frequency, wherein an oscillation preventing means for preventing oscillation at a frequency different from the predetermined frequency is provided in the integrated circuit. 2. The oscillation circuit according to claim 1, wherein said oscillation prevention means is a resistance element connected by wiring in said integrated circuit. 3. The oscillation preventing means according to claim 1, wherein the oscillation preventing means comprises a conductor formed in a conduction hole for electrically connecting different wiring layers in the integrated circuit. Oscillation circuit. 4. The oscillation preventing means alternately serially connects conductors formed in a plurality of conductive holes for electrically connecting different wiring layers in the integrated circuit by the different wiring layers. The oscillation circuit according to claim 1, wherein the oscillation circuit is configured by: