CN1614881A - Audio signal amplifying circuit - Google Patents
Audio signal amplifying circuit Download PDFInfo
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- CN1614881A CN1614881A CN 200410088226 CN200410088226A CN1614881A CN 1614881 A CN1614881 A CN 1614881A CN 200410088226 CN200410088226 CN 200410088226 CN 200410088226 A CN200410088226 A CN 200410088226A CN 1614881 A CN1614881 A CN 1614881A
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Abstract
Provided is an audio signal amplifier circuit which can attenuate a subcarrier signal together with a pilot signal in an audio signal by using the audio signal amplifier circuit having a low-pass type active filter function. An audio signal amplifier circuit 1 is provided with an emitter-grounded transistor 2, a capacitor 8 connected between the base and collector of the transistor 2 and a resistor 9 connected between the collector of the transistor 2 and an alternating grounded point. The low-pass type active filter which has the highest frequency of the audio signal as a cutoff frequency is constituted of the transistor 2, the capacitor 8 and the resistor 9. An IC 18 for stereo signal demodulation circuit has characteristics of selectively attenuating the pilot signal included in the audio signal, and the low-pass type active filter has characteristics of attenuating the subcarrier signal included in the audio signal.
Description
Technical field
The present invention, relating to a kind of amplifier circuit for sound frequency signal that will amplify through the stereo audio signal of stereo demodulation circuit demodulation, particularly can be the amplifier circuit for sound frequency signal that the pilot signal of 19KHz and subcarrier signal that frequency is 38KHz are removed effectively with the frequency that comprises in the stereo audio signal.
Background technology
Now, in FM stereophonic broadcasting, in order to obtain stereo audio signal, carry out the channelized frequencies modulation sending pilot signal and the subcarrier signal that a side frequency of utilization is 19KHz, carry out the timing of separating receiving a side with the channelized frequencies modulation, by frequency is that the pilot signal of 19KHz forms the subcarrier signal that frequency is 38KHz, and uses the subcarrier signal that forms to carry out stereo demodulation.When carrying out this stereo demodulation, in the time of the output stereo audio signal, frequency is that the pilot signal of 19KHz and subcarrier signal that frequency is 38KHz are also exported simultaneously.
At this moment, in general FM stereophone receiver, when obtaining stereo audio signal by stereo demodulation, even comprising pilot signal and the frequency that frequency is 19KHz in the audio signal of stereo demodulation is the subcarrier signal of 38KHz, because frequency is that the pilot signal of 19KHz and subcarrier signal that frequency is 38KHz are outside the renewable frequency band of FM stereophone receiver, with this FM stereophone receiver listen to less than, perhaps, even can listen to, owing to, almost the listener is not produced any influence even regenerate like this for the unclear sound of the low level meaning that is difficult to hear yet.
But, stereo audio signal with stereo demodulation, with the vocal cores recorder that uses dolby system or detect that the record regenerating machine that carries out the high levels such as MD recorder of the judgement between playing music when quiet is regenerated or when recording, the frequency that comprises in the audio signal is the function that the pilot signal of 19KHz or subcarrier signal that frequency is 38KHz can hinder these record regenerating machines, may occur can not regular event situation.
In order to remove this evils, now, in these high-caliber record regenerating machines, in output one side of stereo demodulation circuit, the amplifier circuit for sound frequency signal of the formation that the use amplifier circuit for sound frequency signal is connected with 2 utmost point trap circuits that are called the MPX filter.At this moment, amplifier circuit for sound frequency signal, make the signal level of audio signal audio signal be amplified for the signal level ground of stipulating, 2 utmost point trap circuits, remove by the frequency content decay of not wanting in the audio signal of will amplify, be respectively arranged with trap circuit so have the frequency 19KHz of pilot signal and exist on the frequency 38KHz of subcarrier signal, making frequency like this is the pilot signal of 19KHz and subcarrier signal optionally decay respectively that frequency is 38KHz.
Here, Fig. 3 shows the circuit diagram of an example that output one side at the stereo demodulation circuit is connected with the amplifier circuit for sound frequency signal of amplifier circuit for sound frequency signal and 2 utmost point trap circuits.
As shown in Figure 3, this amplifier circuit for sound frequency signal is connected with stereo demodulation circuit 49, is made up of L channel (L) amplifier circuit for sound frequency signal 30L and R channel (R) amplifier circuit for sound frequency signal 30R.At this moment, left channel audio signal amplifying circuit 30L has: audio signal amplification grounded emitter transistor 31L; The deaccentuator that between the base stage of signal input terminal 46L and transistor 31L, is connected; 2 utmost point trap circuits that between the collector electrode of transistor 31L and signal output terminal 47L, are connected, similarly, right channel audio signal amplifying circuit 30R has: audio signal is amplified and is used grounded emitter transistor 31R; The deaccentuator that connects between the base stage of signal input terminal 46R and transistor 31R; 2 utmost point trap circuits that connect between the collector electrode of transistor 31R and the signal output terminal 47R.
In addition, both sides' deaccentuator, electric capacity 32L, 32R and be connected in series resistance 33L, 33R form by being connected in parallel, both sides' 2 utmost point trap circuits, by the 1st be connected in series inductance 40L, 40R and be connected in parallel electric capacity 41L, 41R, the 2nd inductance 43L, 43R and electric capacity 44L, the 44R that is connected in series in inductance 42L, 42R and the parallel circuits that be connected in series forms.Then, in 2 utmost point trap circuits, the 1st be connected in series the inductance 40L and the electric capacity 41L that is connected in parallel, also have the 1st be connected in series inductance 40R and the electric capacity 41R that is connected in parallel to constitute the 1st trap circuit that frequency 38KHz is carried out trap respectively, the 2nd be connected in series inductance 42L and the inductance 43L and the electric capacity 44L that are connected in series also has the 2nd to be connected in series inductance 42R and the inductance 43R and the electric capacity 44R that are connected in series constitute the 2nd trap circuit that frequency 19KHz is carried out trap respectively.
In addition, the performance plot of the frequency characteristic of illustrated left channel audio signal amplifying circuit 30L and right channel audio signal amplifying circuit 30R in Fig. 4 presentation graphs 3.
In Fig. 4, the audio signal frequency of transverse axis for representing, the audio signal level of the longitudinal axis for representing with dBm with KHz.In this performance plot, solid line represents to comprise the frequency characteristic of 2 utmost point trap circuits, and dotted line represents to remove the frequency characteristic of 2 utmost point trap circuits.
According to the left channel audio signal amplifying circuit 30L of described formation, the following action.At first, in signal input terminal 46, supply with behind the left channel audio signal of stereo demodulation circuit 49 outputs, this audio signal, be endowed the characteristic of postemphasising of regulation during by deaccentuator after, being situated between is applied on the base stage of grounded emitter transistor 31L by coupling capacitance 34L.Grounded emitter transistor 31L makes that this left channel audio signal is that specified signal level ground amplifies, and the left channel audio signal that amplifies is taken out from collector electrode, and being situated between is supplied in 2 utmost point trap circuits by coupling capacitance 39L.2 utmost point trap circuits, shown in the solid line of Fig. 4, making frequency in the left channel audio signal of amplification is that the subcarrier signal of 38KHz is significantly decayed by the 1st trap circuit, the left channel audio signal medium frequency that makes amplification then is that the pilot signal of 19KHz significantly decays by the 2nd trap circuit, in signal output terminal 47L, supply with the left channel audio signal of the amplification of removing subcarrier signal and pilot signal.
In addition, the action of right channel audio signal amplifying circuit 30R, except amplifying signal is a right channel audio signal, also identical with the action of described left channel audio signal amplifying circuit 30L, in signal output terminal 47R, supply with the right channel audio signal of the amplification of removing subcarrier signal and pilot signal by it.
; known amplifier circuit for sound frequency signal with described formation; by using 2 utmost point trap circuits; though subcarrier signal in the audio signal and pilot signal are removed effectively; but constitute the situation of 2 utmost point trap circuits; because 3 inductance and 2 electric capacity are necessary, can not make not only that amplifier circuit for sound frequency signal is that integrated circuit constitutes, also be difficult to realize miniaturization and reduce manufacturing cost.
As avoiding the use of using this 2 utmost point trap circuits, recently, developing a kind ofly, in the stereo demodulation circuit, adding pilot tone and eliminate circuit, and will comprise this pilot tone and eliminate the stereo demodulation circuit IC that the stereo demodulation circuit integral body of circuit constitutes as integrated circuit (IC).This pilot tone is eliminated circuit, because being provided with and making the interior frequency of audio signal circuit is the optionally degenerative negative-feedback circuit of pilot signal of 19KHz, so is that the pilot signal of 19KHz optionally decays by this selectivity negative-feedback circuit with the frequency in the audio signal, even do not use 2 utmost point trap circuits, also can make frequency from the audio signal of stereo demodulation circuit output is that the pilot signal of 19KHz decays significantly.
But, pilot tone is eliminated the built-in stereo demodulation circuit IC of circuit, though eliminating circuit by pilot tone, to make frequency in the audio signal be the pilot signal decay of 19KHz, but owing to can not make frequency in the audio signal is the subcarrier signal decay of 38KHz, so also residual in the audio signal of amplifying frequency is arranged is the subcarrier signal of 38KHz.Therefore, can think that only use built-in pilot tone to eliminate the stereo demodulation circuit IC of circuit, residual subcarrier signal still exerts an influence to high-caliber record regenerating machine, and the function of this high-caliber record regenerating machine can not be brought into play fully.
There is not adoptable patent documentation as prior art
Summary of the invention
The present invention is the product in view of this technical background invention, its purpose is: provide a kind of amplifier circuit for sound frequency signal that makes to have low pass type active filter function, the amplifier circuit for sound frequency signal that only uses amplifier circuit for sound frequency signal just can decay to the pilot signal in the audio signal and subcarrier signal.
In order to realize described purpose, amplifier circuit for sound frequency signal of the present invention is, the amplifier circuit for sound frequency signal that will amplify with the audio signal of IC output from the audio signal demodulator circuit, possess:, export the grounded emitter transistor npn npn of the audio signal of amplifying from collector electrode from stereophonic signal demodulator circuit IC supply audio frequency signal to base stage; The electric capacity that is connected with inter-collector in transistorized base stage; And, transistorized collector electrode with exchange the resistance that is connected between earth point, constitute with transistor and electric capacity and resistance that to make the most significant end frequency of audio signal be the low pass type active filter of cut-off frequency, stereophonic signal demodulator circuit IC, has the characteristic that the pilot signal that comprises in the audio signal of making optionally decays, low pass type active filter has the module of the characteristic of the subcarrier signal decay that comprises in the audio signal of making.
At this moment, the pilot signal in the described module is that frequency is the pilot signal of 19KHz, and described subcarrier signal is that frequency is the subcarrier signal of 38KHz.
In addition, the described low pass type active filter cut-off frequency in the described module is set at 15KHz.
By the present invention, in amplifier circuit for sound frequency signal, by: the grounded emitter transistor npn npn; The electric capacity that is connected with inter-collector in this transistorized base stage; And, this transistorized collector electrode with exchange the resistance that is connected between earth point, it is the low pass type active filter of cut-off frequency that formation makes the most significant end frequency of audio signal, make by the audio signal demodulator circuit and eliminate the subcarrier signal decay that comprises in the circuit audio signal with pilot tone built-in among the IC, even do not use 2 utmost point trap circuits like this, and, only additional simple circuit in amplifier circuit for sound frequency signal just can realize making pilot signal and the abundant simultaneously effect that decays of subcarrier signal in the audio signal.
Description of drawings
Fig. 1 represents to be used to implement the circuit diagram of the best mode of amplifier circuit for sound frequency signal of the present invention.
Fig. 2 represents to comprise the performance plot with the frequency characteristic of the left channel audio signal amplifying circuit of IC and right channel audio signal amplifying circuit of illustrated stereo demodulation circuit among Fig. 1.
Fig. 3 is the circuit diagram of an example of output one side that is illustrated in the stereo demodulation circuit amplifier circuit for sound frequency signal that connected amplifier circuit for sound frequency signal and 2 utmost point trap circuits.
The performance plot of the frequency characteristic of illustrated left channel audio signal amplifying circuit and right channel audio signal amplifying circuit in Fig. 4 presentation graphs 3.
Among the figure: 1L～left channel audio signal amplifying circuit 1R～right channel audio signal amplifying circuit 2L, 2R～grounded emitter transistor npn npn 3L, 3R～electric capacity 4L is connected in parallel, 4R～resistance 5L is connected in series, 5R, 11L, 11R～coupling capacitance 6L, 6R, 7L, the bigoted resistance 8L of 7R～base stage, 8R～feedback capacity 9L, 9R～collector resistance 10L, 10R～emitter resistance 12L, 12R～impedance matching resistance 13L, 13R～signal output terminal 14L, 14R～signal input terminal 15L, 15R～power supply terminal 18～stereo demodulation circuit is eliminated circuit with IC 19～pilot tone
Embodiment
Below, embodiments of the present invention are described with reference to accompanying drawing.
Fig. 1 represents to be used to implement the circuit diagram of the best mode of amplifier circuit for sound frequency signal of the present invention.
As shown in Figure 1, the amplifier circuit for sound frequency signal of this execution mode, the stereo demodulation circuit of eliminating circuit 19 with built-in pilot tone is with the configuration that is connected of the outlet side of IC18, by left channel audio signal amplifying circuit 1L and right channel audio signal amplifying circuit 1R formation.At this moment, left channel audio signal amplifying circuit 1L has: grounded emitter transistor npn npn 2L; The deaccentuator that between the base stage of signal input terminal 15L and transistor 2L, connects; And the low pass type active filter circuit that between the base stage of transistor 2L and collector electrode, connects.Similarly, right channel audio signal amplifying circuit 1R has: grounded emitter transistor npn npn 2R; The deaccentuator that between the base stage of signal input terminal 15R and transistor 2R, connects; And the low pass type active filter circuit that between the base stage of transistor 2R and collector electrode, connects.
Then, both sides' deaccentuator, electric capacity 3L, 3R and be connected in series resistance 4L, 4R form by being connected in parallel.In addition, both sides' low pass type active filter circuit, the feedback capacity 8L, the 8R that are connected with inter-collector by the base stage of transistor 2L, 2R, the collector resistance 9L, the 9R that are connected with collector electrode with transistor 2L, 2R constitute.At this moment, both sides' low pass type active filter makes the highest frequency of audio signal frequency band, and for example frequency 15KHz is cut-off frequency ground, selects the resistance value of capability value and collector resistance 9L, the 9R of feedback capacity 8L, 8R respectively.
Also have, transistor 2L, between base stage and deaccentuator, connect coupling capacitance 5L, between base stage and power supply terminal 15L and between base stage and earth point, be connected base biasing resistor 6L, 7L respectively, between emitter and earth point, be connected emitter resistance 10L, between collector electrode and signal output terminal 13L, connect coupling capacitance 11L.Similarly, transistor 2R, between base stage and deaccentuator, connect coupling capacitance 5R, between base stage and power supply terminal 15R and between base stage and earth point, be connected base biasing resistor 6R, 7R respectively, between emitter and earth point, be connected emitter resistance 10R, between collector electrode and signal output terminal 13R, connect coupling capacitance 11R.
In addition, between signal output terminal 13L and earth point, be connected with impedance matching resistance 12L.Similarly, between signal output terminal 13R and earth point, be connected with impedance matching resistance 12R.
Next, Fig. 2 represents to comprise the performance plot with the frequency characteristic of the left channel audio signal amplifying circuit 1L of IC18 and right channel audio signal amplifying circuit 1R of illustrated stereo demodulation circuit among Fig. 1, solid line is their composite characteristic, and dotted line is to be used for the characteristic of having only left channel audio signal amplifying circuit 1L and right channel audio signal amplifying circuit 1R that comparison is represented.
Here, describe with the action of the amplifier circuit for sound frequency signal of IC18 comprising illustrated stereo demodulation circuit among Fig. 1 and with illustrated performance plot among Fig. 2.
At first, supplying with should be by the stereophonic signal of demodulation from its front stage circuits (not having diagram Fig. 1) in stereo demodulation circuit usefulness IC18, stereo demodulation circuit IC18, with the subcarrier signal of the frequency 38KHz that obtains from the pilot signal of frequency 19KHz stereophonic signal that should demodulation is carried out demodulation, and produce the stereo audio signal of demodulation.The stereo audio signal that obtain this moment for left channel audio signal and 2 audio signals of right channel audio signal, has wherein comprised the pilot signal of frequency 19KHz and the subcarrier signal of frequency 38KHz.Afterwards, left channel audio signal and right channel audio signal, being fed into pilot tone respectively eliminates in the circuit 19, so the pilot signal of frequency 19KHz is by optionally negative feedback, the pilot signal of frequency 19KHz is decayed significantly, the left channel audio signal of significantly being decayed with the pilot signal of the L channel output 20L output frequency 19KHz of IC18 from the stereo demodulation circuit, from the stereo demodulation circuit with the R channel output 20R of the IC18 pilot signal of the output frequency 19KHz right channel audio signal of significantly being decayed similarly.Then, the left channel audio signal of output is fed among the signal input terminal 14L of left channel audio signal amplifying circuit 1L, and the right channel audio signal of output is fed among the signal input terminal 14R of right channel audio signal amplifying circuit 1R.
Next, left channel audio signal amplifying circuit 1L, after being supplied to left channel audio signal among the signal input terminal 14L, give the characteristic of postemphasising of regulation to left channel audio signal in deaccentuator after, left channel audio signal is situated between to be supplied in the base stage of grounded emitter transistor 2L by coupling capacitance 5L.Grounded emitter transistor 2L, the left channel audio signal that order is supplied with is that specified signal level ground amplifies, and the left channel audio signal that amplifies is taken out from collector electrode.At this moment, grounded emitter transistor 2L, by the low pass type active filter circuit that is connected with inter-collector in its base stage, shown in the dotted line in the illustrated performance plot of Fig. 2, making the frequency in the left channel audio signal of amplification is the subcarrier signal decay of 38KHz.
On the other hand, stereo demodulation IC18, eliminate circuit 19 by built-in pilot tone, making frequency in the left channel audio signal that supplies among the left channel audio signal amplifying circuit 1L is that the pilot signal of 19KHz is exported with the state of significantly decay, be launched the left channel audio signal of the amplification that the collector electrode of utmost point grounding transistor 2L derives, shown in the solid line in the illustrated performance plot in using Fig. 2, frequency is that the pilot signal of 19KHz and subcarrier signal that frequency is 38KHz are attenuated simultaneously, supplies with frequency and be the left channel audio signal that the pilot signal of 19KHz and subcarrier signal that frequency is 38KHz have been decayed in signal output terminal 13L.
In addition, in amplifier circuit for sound frequency signal 1R, after being supplied to right channel audio signal among the signal input terminal 14R, give the characteristic of postemphasising of regulation to right channel audio signal in deaccentuator after, also right channel audio signal being situated between is supplied in the base stage of grounded emitter transistor 2R by coupling capacitance 5R.Grounded emitter transistor 2R, the right channel audio signal that order is supplied with is that specified signal level ground amplifies, and the right channel audio signal that amplifies is taken out from collector electrode.At this moment, grounded emitter transistor 2R, by the low pass type active filter circuit that is connected with inter-collector in its base stage, shown in the dotted line in the illustrated performance plot of Fig. 2, also making the frequency in the right channel audio signal of amplification is the subcarrier signal decay of 38KHz.
At this moment, stereo demodulation IC18, eliminate circuit 19 by built-in pilot tone, making frequency in the right channel audio signal that supplies among the right channel audio signal amplifying circuit 1L is that the pilot signal of 19KHz is exported with the state of significantly decay, be launched the right channel audio signal of the amplification that the collector electrode of utmost point grounding transistor 2R derives, shown in the solid line in the illustrated performance plot in using Fig. 2, frequency is that the pilot signal of 19KHz and subcarrier signal that frequency is 38KHz are attenuated simultaneously, supplies with frequency and be the right channel audio signal that the pilot signal of 19KHz and subcarrier signal that frequency is 38KHz have been decayed in signal output terminal 13R.
Like this, if by the amplifier circuit for sound frequency signal in this execution mode, do not use 2 utmost point trap circuits that in known sort circuit, use, and, only in amplifier circuit for sound frequency signal, add the simple low pass type active filter circuit that constitutes, pilot signal and subcarrier signal in the audio signal are side by side fully decayed, and can obtain not only can integrated circuit, can also realize miniaturization and reduce the amplifier circuit for sound frequency signal of manufacturing cost.
Moreover, in the described execution mode, enumerate the low pass type active filter that will be connected with inter-collector in the base stage of transistor 2L, 2R, with feedback capacity 8L, 8R, the example that constitutes with collector resistance 9L, 9R describes, but the low pass type active filter circuit that uses among the present invention is not limited to this formation, only otherwise with circuit complicated, also can add the unit beyond these unit.
In addition, in said embodiment, the example of enumerating the cut-off frequency that makes low pass type active filter and be 15KHz describes, but the cut-off frequency of the low pass type active filter circuit that uses among the present invention, be not limited to 15KHz, can certainly be chosen as near the frequency of frequency 15KHz for the frequency band of corresponding audio signal.
Also have, in the described true mode, be frequency 19KHz with the pilot signal, subcarrier signal describes for frequency 38KHz, but pilot signal among the present invention and subcarrier signal are not limited to the situation of 19KHz and 38KHz, also can be other frequencies of the classification of corresponding FM broadcast singal certainly.
Claims (3)
1. amplifier circuit for sound frequency signal, to amplify with the audio signal of IC output from the audio signal demodulator circuit, it is characterized in that: have: base stage is supplied to from the audio signal of described stereophonic signal demodulator circuit with IC, by the grounded emitter transistor npn npn of the audio signal of collector electrode output through amplifying;
The electric capacity that is connected with inter-collector in described transistorized base stage; And
Described transistorized collector electrode with exchange the resistance that is connected between earth point,
With described transistor, described electric capacity and described resistance, the most significant end frequency that constitutes with audio signal is the low pass type active filter of cut-off frequency,
Described stereophonic signal demodulator circuit IC has the characteristic that the pilot signal that comprises in the audio signal of making optionally decays,
Described low pass type active filter has the characteristic of the subcarrier signal decay that comprises in the audio signal of making.
2. amplifier circuit for sound frequency signal according to claim 1 is characterized in that: described pilot signal is that frequency is the pilot signal of 19KHz,
Described subcarrier signal is that frequency is the subcarrier signal of 38KHz.
3. amplifier circuit for sound frequency signal according to claim 1 and 2 is characterized in that: described low pass type active filter cut-off frequency is set at 15KHz.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2003378565A JP2005142924A (en) | 2003-11-07 | 2003-11-07 | Audio signal amplifier circuit |
| JP2003378565 | 2003-11-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN1614881A true CN1614881A (en) | 2005-05-11 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 200410088226 Pending CN1614881A (en) | 2003-11-07 | 2004-10-21 | Audio signal amplifying circuit |
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| Country | Link |
|---|---|
| JP (1) | JP2005142924A (en) |
| CN (1) | CN1614881A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101359970B (en) * | 2008-09-28 | 2011-07-27 | 无锡市晶源微电子有限公司 | Automobile radio circuit having pilot signal suppression |
| CN106257829A (en) * | 2015-06-22 | 2016-12-28 | 飞思卡尔半导体公司 | There is the many restriction RF substrates below bias line and the RF circuit in conductive material space |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7800435B2 (en) * | 2006-12-11 | 2010-09-21 | Fairchild Semiconductor Corporation | Audio filter using a diode connected MOSFET |
-
2003
- 2003-11-07 JP JP2003378565A patent/JP2005142924A/en active Pending
-
2004
- 2004-10-21 CN CN 200410088226 patent/CN1614881A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101359970B (en) * | 2008-09-28 | 2011-07-27 | 无锡市晶源微电子有限公司 | Automobile radio circuit having pilot signal suppression |
| CN106257829A (en) * | 2015-06-22 | 2016-12-28 | 飞思卡尔半导体公司 | There is the many restriction RF substrates below bias line and the RF circuit in conductive material space |
| CN106257829B (en) * | 2015-06-22 | 2021-06-22 | 恩智浦美国有限公司 | RF circuit with multiple defined RF substrates and conductive material voids under bias lines |
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| Publication number | Publication date |
|---|---|
| JP2005142924A (en) | 2005-06-02 |
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Open date: 20050511 |