JP2001102875A - Semiconductor amplifier circuit and semiconductor electret capacitor microphone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to be hardly affected by a burst noise. SOLUTION: This circuit is provided with a voltage converting circuit 10 for inputting a fine signal α and outputting the relevant signal as a voltage signal β and an amplifier circuit for inputting the voltage signal β and amplifying out the relevant signal, and the voltage converting circuit 10 and the amplifier circuit 20 are formed inside the same semiconductor chip C. Namely, since the input terminal of the amplifier circuit 20 is hidden inside the semiconductor chip C, the burst noise is hardly inputted to the amplifier circuit 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor amplifying circuit which is hardly affected by burst noise and a semiconductor electret condenser microphone used for a cellular phone or the like.

[0002]

2. Description of the Related Art A semiconductor electret condenser microphone is often used as a microphone of a digital portable telephone or the like.

As shown in FIG. 10, a conventional semiconductor electret condenser microphone is a polymer film formed into an electret, and a vibrating film 2 adhered to a ring 1 and a back surface arranged opposite to the vibrating film 2. The vibrating membrane 2 and the back electrode 3 are interposed between the pole 3, the back electrode 3 and the ring 1.
And a back electrode holder 5 for holding the back electrode 3, IC chips 61 and 62 mounted on a printed circuit board 8, and a case 7 for accommodating them. It has a basic structure. In the drawing, reference numeral 9 denotes a front cross.

A capacitor is formed by the vibrating membrane 2 and the back electrode 3, and the sound is converted into an audio signal by utilizing the fact that the capacitance of the capacitor changes due to the vibration of the vibrating membrane 2, and the signal is amplified. Output. As a circuit for amplifying the signal, a semiconductor amplifier circuit as shown in FIG. 11 is often used.

The circuit comprises a voltage conversion circuit A for converting an audio signal into a voltage signal and outputting the voltage signal, and an amplifier circuit B for amplifying and outputting the voltage signal input from the voltage conversion circuit A. The IC chip 61 has a voltage conversion circuit A,
Each of the IC chips 62 has an amplifier circuit B formed therein. Vdd is a power supply voltage terminal, GND is a ground voltage terminal, Vout1 is an output terminal of the voltage conversion circuit A, Vout
Denotes output terminals of the amplifier circuit B.

[0006]

However, in the case of the above conventional example, there is a disadvantage that the semiconductor amplifier circuit is easily affected by burst noise. That is, a high frequency oscillator provided in a digital mobile phone (TDMA system) is a source of burst noise (RF burst signal),
Burst noise radiated from the high-frequency oscillator enters a power supply line or a wiring line, and as a result, a large burst noise component (burst operation frequency: 200 to 400 Hz) appears in an output signal of the semiconductor amplifier circuit. In particular, since the input signal line of the amplifier circuit B is exposed, and the burst noise that enters the line is amplified by the amplifier circuit B, it is necessary to reduce the noise of the semiconductor electret condenser microphone, and thus the mobile phone and the like. It is a big problem.

Although providing a noise-blocking capacitor at the output stage of the amplifier circuit 20 is effective for low-level burst noise, it is not always sufficient as a noise countermeasure and increases the number of parts. This is an obstacle to cost reduction.

The present invention has been made in view of the above background, and an object of the present invention is to provide a semiconductor amplifier circuit and a semiconductor electret condenser microphone which are hardly affected by burst noise.

[0009]

A semiconductor amplifier circuit according to the present invention is a circuit for amplifying and outputting a small signal, comprising a voltage conversion circuit which receives a small signal and outputs the signal as a voltage signal. And an amplifier circuit to which a voltage signal output from the voltage conversion circuit is input and amplify and output the signal, and that the voltage conversion circuit and the amplifier circuit are formed in the same semiconductor chip. Features.

In such a configuration, since the input terminal of the amplifier circuit is hidden in the semiconductor chip, it becomes difficult for burst noise to be input to the amplifier circuit.

As the voltage conversion circuit, a junction type or MO having the source grounded and the small signal input to the gate is used.
It is preferable to use an S-type FET and a resistor that is connected between the drain of the FET and the power supply line and has a resistance that converts the drain current of the FET into a voltage and outputs the voltage as a voltage signal.

As the voltage conversion circuit, it is more preferable that a small signal is input to the gate and the source is connected to the junction-type or MOS-type first FET, and between the drain of the first FET and the power supply line. Is connected between the source and the drain, and outputs a source voltage as a voltage signal.
And a reference voltage generation circuit that generates a reference voltage by using the power supply voltage on the power supply line as an input and outputs the reference voltage to the gate of the second FET.

In such a configuration, if the power supply voltage fluctuates due to burst noise entering the power supply line or the like, the source voltage of the second FET fluctuates, but the second FET fluctuates.
Since the reference voltage input to the gate of the second FET also changes at the same time, the degree of change in the source voltage of the second FET is smaller than that of the power supply voltage. Therefore, even if the burst noise enters the power supply line or the like, the burst noise input to the amplifier circuit is reduced.

It is desirable that the amplifier circuit be provided with a gain adjustment circuit for making the gain of the circuit externally adjustable. This is because variations in the characteristics of the voltage conversion circuit can be absorbed by adjusting the gain of the amplifier circuit.

More preferably, it is desirable to provide a surge protection capacitance formed using a transistor between the output of the amplifier circuit and the power supply line and / or the ground line. This is because even if a large burst noise component appears in the output of the amplifier circuit under the influence of the burst noise, this component is prevented by the capacitance.

In the semiconductor electret condenser microphone of the present invention, a capacitor is formed by the vibrating film and the back electrode, and the sound is converted into a sound signal by utilizing the fact that the capacitance of the capacitor changes due to the vibration of the vibrating film. A device for amplifying and outputting the signal, wherein the semiconductor amplifier is used for amplifying the audio signal.

The semiconductor electret condenser microphone preferably has a structure in which an electrode layer serving as the back electrode is provided on the upper surface side of the semiconductor chip on which the semiconductor amplifier circuit is formed.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a semiconductor amplifier circuit,
FIG. 2 is a circuit diagram for explaining a modification of the semiconductor amplifier circuit, FIG. 3 is a schematic sectional view of a semiconductor electret condenser microphone, FIG. 4 is a schematic exploded perspective view of a case of the microphone, and FIG. FIG. 6B is a schematic bottom view of the same case, FIG. 6 is a schematic plan view of a spacer layer of the microphone, FIG. 7 is a schematic sectional view of a diaphragm of the microphone, FIG. Is a circuit diagram showing the electrical connection relationship with the microphone in the circuit shown in FIG. 2, and FIG. 9 is a graph showing the relationship between the level of burst noise contained in the output signal of the circuit and the frequency.

The semiconductor amplifier circuit given here as an example is as follows.
A circuit for amplifying and outputting a small audio signal γ detected in a semiconductor electret condenser microphone for a mobile phone. A voltage to which an audio signal is input as shown in FIG. 1 and the signal is output as a voltage signal The basic configuration includes a conversion circuit 10 and an amplifier circuit 20 to which a voltage signal is input and which amplifies the signal and outputs it as an audio signal γ. The most characteristic feature of this semiconductor amplifier circuit is that the voltage conversion circuit 10 and the amplifier circuit 20 are formed in the same semiconductor chip C.

A power supply voltage terminal Vdd for inputting a power supply voltage, a ground voltage terminal GND, an input terminal Vin for inputting an audio signal α, are provided on the outer surface of the semiconductor chip C.
Output terminals Vout for outputting the audio signal γ are provided. In the figure, L indicates a power supply line, and G indicates a ground line (solid earth pattern). Hereinafter, each constituent circuit will be described.

The voltage conversion circuit 10 is grounded at the source and has an FET 11 having an audio signal α input to its gate,
A resistor 12 connected between the drain of the FET 11 and the power supply line L for converting the drain current of the FET 11 into a voltage and outputting it as a voltage signal β, and a gate voltage of the FET 11 of 0
And a bias circuit 13 for biasing to V. As the FET 11, an N-channel junction type junction FET is used.
A CMOS FET may be used. Further, a diode or a resistor of the order of giga is used as the bias circuit 13.

As the amplifier circuit 20, an operational amplifier 21 having a high input impedance and a low output impedance is used, and a voltage signal β is non-inverted and amplified to generate an audio signal γ.

In the semiconductor amplifier circuit having the above-described structure,
The operation will be described. A via is connected to the gate of FET11.
Since the switching circuit 13 is provided, the gate of the FET 11 is
Gate-source voltage V_GSBecomes 0V. V_GS
= 0, the drain current I of the FET 11_DTo I_DSSWhen
When expressed as_DSSAnd the pinch-off voltage V of the FET 11 _P
Is as shown in the following equation. Β is FET1
This is a constant determined by the gate size of 1.

[0024]

(Equation 1)

Further, the relationship between the current change [Delta] I _D of the drain current I _D of the voltage change [Delta] V _IN and FET11 audio signal α when the V _GS = 0 is as shown in the following equation.

[0026]

(Equation 2)

Therefore, ΔI _D is represented by the following equation by using Equations 2 and 1.

[0028]

(Equation 3)

[0029] That is, the voice signal α is changed by [Delta] V _IN, the drain current I _D of the FET11 is changed by [Delta] I _D. Since the input impedance of the operational amplifier 21 is very high and the drain current _ID flows through the resistor R12,
The input voltage Va of the operational amplifier 21 changes as follows.
Note that the resistance value of the resistor R12 is represented as R.

[0030]

(Equation 4)

Drain current I _D of FET11 when the [0031] V _GS = 0 is because it is I _DSS, the DC component of Va is expressed as follows. The power supply voltage is also represented as V _DD .

[0032]

(Equation 5)

When the audio signal α is input to the voltage conversion circuit 10, a voltage Va proportional to the signal is generated in the circuit as shown in FIGS. 4 and 5, and this voltage is input to the amplifier circuit 20 as a voltage signal β. And an audio signal γ is generated.

In such a semiconductor amplifier circuit, unlike the conventional example, the input terminal of the amplifier circuit 20 is hidden in the semiconductor chip C, so that burst noise generated by the high frequency oscillator of the mobile phone is generated. Voltage signal β
There is little intrusion. As a result, even if the voltage signal β is amplified by the amplifier circuit 20, the burst noise component included in the amplified audio signal γ becomes very small.

Incidentally, the pinch-off voltage (VP) of the components used in the voltage conversion circuit 10, especially the FET 11, usually varies from product to product. Since the DC component of the voltage signal β is proportional to the square of the FET 11 pinch-off voltage (VP) as shown at 75, the level of the audio signal γ greatly varies from product to product. Since the voltage conversion circuit 10 and the amplifier circuit 20 are formed in the same semiconductor chip C, it is impossible to adjust the level of the audio signal γ by a method of selecting components.

As a countermeasure, it is preferable to provide a gain adjustment circuit 30 for enabling the gain of the amplifier circuit 20 to be adjusted from the outside, as shown by a dotted line in the figure. The circuit has a configuration in which the amount of feedback of the amplifier circuit 20 is adjusted according to the voltage input via a gain adjustment terminal Gadj provided on the outer surface of the semiconductor chip C, and the gain of the amplifier circuit 20 is changed. ing. Further, the input operation range of the amplifier circuit 20 may be widened.

Although the semiconductor amplifier circuit shown in FIG. 1 is very effective against burst noise radiated from a high-frequency oscillator of a portable telephone, it is effective against burst noise entering through a power supply line L, a ground line G and the like. It is not effective for them. When burst noise entering the power supply line L or the like is also a problem, the semiconductor amplifier circuit shown in FIG. 2 may be used.

A voltage conversion circuit 10 'is significantly different from the circuit shown in FIG. The circuit includes an FET 11 (first F1) having a source grounded and an audio signal α input to a gate.
An FET 13 (corresponding to a second FET) having a source-drain connected between the drain of the FET 11 and the power supply line L and outputting a source voltage as a voltage signal β; Power supply voltage on L (V
dd) to generate a reference voltage Vref,
3 and a reference voltage generation circuit 14 that outputs the reference voltage to the third gate. The FET 11 and the FET 13 are formed on the same semiconductor manufacturing process, and both FEs are formed.
T has the same structure.

The connection between the circuit and the semiconductor electret condenser microphone is as shown in FIG. This is the same for the circuit shown in FIG.

The reference voltage generation circuit 14 supplies the power supply voltage (Vd
d) is divided by the resistors R141 and R142 to generate the reference voltage Vref.

Further, between the output of the amplifier circuit 20 and each of the power supply line L and the ground line G, surge protection capacitances 41 and 42 formed using transistors are provided, respectively. As the capacitances 41 and 42, enhancement-type junction type FETs are used, and they are connected as shown in the drawing to have a large gate area and have a parasitic capacitance of 2 PF or more.
The rest is exactly the same as the circuit shown in FIG.

The operation of the semiconductor amplifier configured as described above will be described. Similar to the circuit, the relationship between the current change [Delta] I _D of the drain current I _D of the voltage change [Delta] V _IN and FET11 audio signal α when the V _GS = 0 is as shown in the following equation. Note that β1 is a constant determined by the gate size of the FET 11.

[0043]

(Equation 6)

[0044] When the drain current I _D of the FET11 is changed, but also changes in the same manner the drain current I _D of the FET13, since the reference voltage Vref is input to the gate of FET13, between the gate and the source of FET13 voltage V _GS changes according to the drain current _ID of the FET 11. The relationship between the two is as follows. Β2 is FE
This is a constant determined by the gate size of T13.

[0045]

(Equation 7)

The change in the input voltage of the operational amplifier 21 is ΔVa
Then, .DELTA.Va is expressed by the following formulas by Expressions 6 and 7.

[0047]

(Equation 8)

The DC component of Va is expressed by the following equation.

[0049]

(Equation 9)

Since Vref = V _DD / 2 and β1 = β2, the gate-source voltage V
_GS becomes zero. Therefore, the voltage signal β and the audio signal γ change around V _DD / 2. Except for this point, FIG.
The operation is basically the same as the circuit shown in FIG. However, even if burst noise enters the power supply line L or the like, a large burst noise component does not appear in the audio signal γ for the following reason.

When V _DD changes under the influence of burst noise, Vref similarly changes accordingly. However, as shown in Expression 9, since the signs of V _DD and Vref are opposite, Va does not change so much even if V _DD changes. Moreover, even if a surge is applied to V _{DD due} to burst noise, capacitances 41 and 42 for surge protection are provided.
Absorbs surge. As a result, a large burst noise component does not appear in the audio signal γ.

A mobile phone is provided with a high-frequency oscillator for transmitting and receiving radio waves, which has conventionally been a source of burst noise and has had a great influence on semiconductor electret condenser microphones.
When the semiconductor amplifier circuit shown in FIG. 1 or 2 is used for the semiconductor electret condenser microphone shown in FIG. 5,
Since the semiconductor amplifier circuit itself is very resistant to burst noise, it is possible to reduce the noise of the microphone, and eventually the mobile phone.

The semiconductor amplifier circuit shown in FIG. 1 or FIG.
The same applies to the semiconductor electret condenser microphones shown in FIGS. Hereinafter, the structure of the microphone will be described with reference to the drawings.

As shown in FIG. 3, the microphone is
Alternatively, a semiconductor chip 100 on which the semiconductor amplifier circuit shown in FIG. 2 is formed, and an insulating layer 130 on the surface of the semiconductor chip 100
, An insulating layer 150 formed on the electrode layer 140, a vibrating film 200 attached to the ring 230, and a vibration interposed between the ring 230 and the insulating film 150. The basic structure includes a spacer layer 170 for opening a space 180 between the film 200 and the insulating film 150, and a case 300 for accommodating them.

The electrode layer 140 facing the vibrating membrane 200 functions as the back electrode 3 of the semiconductor electret condenser microphone shown in FIG. Vibrating membrane 200
Is grounded by a method described later, while the electrode layer 1
40 is a wiring (not shown) formed on the insulating layer 130,
It is connected to an electrode (input terminal Vin: not shown) formed on the surface of the semiconductor chip 100. In short, when the vibrating film 200 vibrates, the electric charge charged in the electrode layer 140 changes, and the voltage at this time becomes the audio signal α.

The case 300 includes a case body 310 having a recess 330 into which the semiconductor chip 100 is fitted,
And a lid 320 for closing the case body 310.

As shown in FIG. 4, the case body 310 has four substantially frame-shaped members, that is, a first layer 311, a second layer 312,
The third layer 313 and the fourth layer 314 are stacked. First layer 311, second layer 313, and fourth layer 31
4 have the same outer dimensions, and when they are stacked, one substantially rectangular parallelepiped is formed. The first layer 311 is a conductive adhesive, the second layer 313,
Layer 313 and fourth layer 314 are ceramic.

On the surface side of the lowermost fourth layer 314, a grounding conductive layer 3 such as nickel plating or aluminum plating is formed.
14B are formed. A signal output terminal conductive layer 314E and a power supply terminal conductive layer 314F are formed on the two concave portions 314C and 314D formed on the side surface of the fourth layer 314, and on the front surface side and the rear surface side, respectively.

The center of the fourth layer 314 has a back room 3
There are formed 50 concave portions 314A. Recess 314
The dimension of A is set smaller than the semiconductor chip 100 so that the semiconductor chip 100 does not enter.

The third layer 313 laminated on the fourth layer 314
An opening 313A is opened at the center of the third layer 313. When the third layer 313 is laminated on the fourth layer 314, the third layer 313 is formed.
Of the conductive layer 314B of the fourth layer 314 from the opening 313A of FIG.
Can be seen. Except for the opening 313A, a grounding conductive layer 313B such as nickel plating or aluminum plating is formed on the surface side of the third layer 313. The two concave portions 313C and 313D formed on the side surface of the third layer 312 and the front and back surfaces thereof have a signal output terminal conductive layer 313E and a power supply terminal conductive layer 313F.
Are respectively formed. These are a signal output terminal conductive layer 314E and a power supply terminal conductive layer 314F of the fourth layer 314.
And is to be connected to.

The opening 313A of the third layer 313 is inserted into the semiconductor chip 1 so that the semiconductor chip 100 is fitted.
The size is set slightly larger than 00.

The second layer 312 laminated on the third layer 313
An opening 312A larger than the opening 313A is opened at the center of the third layer 312. When the second layer 312 is stacked on the third layer 313, the third layer 33
The thirteen conductive layers 313B can be seen. The surface of the second layer 312 is connected to the electrode 191 of the semiconductor chip 100 by a bonding wire 190.
One pad is formed.

The three pads correspond to the conductive layers 313B,
14B, the signal output pad 312E to which the signal output terminal conductive layers 313E and 314E are connected, and the power supply terminal conductive layers 313F and 314.
F is a power supply pad 312F connected to F. The grounding pad 312G is formed in the corner recess 312K, and the signal output pad 312E and the power supply pad 312F are formed in the two recesses 312C and 312D on the side surface and on the front side and the back side.

The central portion of the first layer 311 laminated on the second layer 312 has an opening 31 larger than the opening 312A.
1A has been established.

As shown in FIGS. 3, 4 and 5, the case body 310 is composed of a first layer 311, a second layer 312, and a third layer 31.
The third and fourth layers 314 are laminated and fired. One side surface of the concave portion 330 of the case main body 310 is stepped due to the dimensional relationship among the opening 311A of the first layer 311, the opening 312A of the second layer 312, and the opening 313A of the third layer 313. Note that the second layer 312 and the third layer 3
13 can be integrated into a three-layer structure as a whole.

As shown in FIG. 3, a ring-shaped convex 321 for pressing the ring 230 to which the vibration film 200 is attached is formed on the back side of the lid 320 that closes the case body 310. Sound hole 32 near the center
2 have been established.

The semiconductor chip 100, the insulating layer 130, the electrode layer 140, the insulating film 150, and the spacer layer 170 are formed by using an existing semiconductor process technology.
The electrode layer 140 is made of aluminum, and the insulating film 150 is made of TiN, and is formed by vapor deposition or the like. Spacer layer 170
Is a polyimide resin, which is formed by etching or the like. Note that when a material having high corrosion resistance is used as the electrode layer 140, the insulating film 150 does not need to be particularly provided. In FIG. 3, reference numeral 110 denotes an element which constitutes the voltage conversion circuit 10 and the like formed in the semiconductor chip 100.

A substantially ring-shaped spacer layer 170 is formed on the insulating film 150 as shown in FIG. Cuts 171 are formed in the spacer layer 170 as shown in the figure. The space 180 and the back room 350 are
The cutout 171 is communicated via the communication path 360 (see FIG. 3).

As shown in FIG. 3, on the surface of the semiconductor chip 100 where the insulating layer 130 and the like are not laminated,
An electrode 191 (corresponding to only one of the ground voltage terminal GND, the output terminal Vout, and the power supply voltage terminal Vdd in the figure) is formed.
Using 0 or the like, the pad is electrically connected to the ground pad 312G, the signal output pad 312E, and the power supply pad 312F formed on the case main body 310.

As the vibrating film 200, a film formed by electreting a polymer FEP film 210 having an electrode film 220 formed on one side as shown in FIG. 2 is used here.
Polymer FEP film 2 having a thickness of 5 μm to 12.5 μm
The electrode film 220 is formed by evaporating nickel to a thickness of about 400 ° on the front surface of the substrate 10. Then, by subjecting the side on which the electrode film 220 is not formed, that is, the back side, to corona irradiation, EB irradiation, and other polarization treatments, the polymer FEP film 210 is semipermanently charged with an electric charge to form an electret.

The electrode 1220 may be formed by depositing aluminum to a thickness of about 400 ° and laminating an insulating coat of polyimide or the like to enhance environmental resistance. Alternatively, aluminum and nickel may be deposited.

The vibrating membrane 200 is mounted on a ring 230 of brass, stainless steel or the like. Vibrating membrane 2
The electrode film 220 on the ring 230 and the case 300
Are grounded via the lid 320 and the grounding conductive layer of the case body 310. Conductivity is ensured between the ring 230, the lid 320, and the case body 310 by a conductive adhesive.

In the semiconductor electret condenser microphone having the above-described structure, a capacitor is formed by the vibrating film 200 and the electrode layer 140, and the sound is generated by utilizing the fact that the capacitance of the capacitor changes due to the vibration of the vibrating film 200. Into an audio signal α. When amplifying the audio signal α, the semiconductor amplifier circuit shown in FIG. 1 or 2 is used. Compared to the semiconductor electret condenser microphone shown in FIG.
There are various advantages such as a small number of parts and a reduction in size.

The semiconductor electret condenser microphone shown in FIG. 3 to FIG. 7 is installed in a PW (Parallel Wired) cell, and under a 400 Hz burst electric field of 900 MHz, about 10 V / m (at the time of continuous wave), the semiconductor shown in FIG. The audio signal γ output from the amplifier circuit was measured with a FET analyzer. The graph of FIG. 9A shows the measurement result of the circuit. FIG. 9B shows a measurement result of the microphone with respect to the semiconductor amplifier circuit shown in FIG. Note that similar characteristics are obtained for the semiconductor amplifier circuit shown in FIG.

In the conventional semiconductor amplifier shown in FIG.
There is a clear peak at 400 Hz and its harmonics. No noise reduction was observed even when a 35 pF capacitor was externally connected. On the other hand, in the semiconductor amplifier circuit of the present invention shown in FIG. 8, such a noise peak is not observed. 1900MHz, about 10V / m (continuous wave) 40
Similar results were obtained when measured under a 0 Hz burst electric field. Therefore, experiments have confirmed that there is no problem regarding RF burst noise not only in mobile phones but also in PHS applications.

The semiconductor amplifier circuit of the present invention can be applied not only to the semiconductor electret condenser microphone but also to other applications. In addition, as long as the voltage conversion circuit and the amplifier circuit perform the same function, any circuit configuration may be used.

In the semiconductor electret condenser microphone of the present invention, a capacitor is formed by the diaphragm and the back electrode, and the sound is converted into an audio signal by utilizing the fact that the capacitance of the capacitor changes due to the vibration of the diaphragm. As long as the configuration is such that the signal is amplified and output, any configuration can be similarly applied.

[0078]

As described above, according to the semiconductor amplifier circuit of the first or second aspect of the present invention, the signal input terminal of the amplifier circuit is hidden in the semiconductor chip, so that it is difficult for burst noise to be input to the amplifier circuit. Therefore, it is less susceptible to the effects of burst noise, which is advantageous in reducing noise.

In the case of the semiconductor amplifier circuit according to the third aspect of the present invention, even if burst noise is mixed in the power supply line or the like, the burst noise input to the amplifier circuit is reduced. Is more difficult to receive.

In the case of the semiconductor amplifier circuit according to the fourth aspect of the present invention, since the variation in the characteristics of the voltage conversion circuit can be absorbed by adjusting the gain of the amplifier circuit, the adjustment of the circuit is simplified. And there are advantages in this regard.

According to the semiconductor amplifier circuit of the present invention, even if a large burst noise component appears in the output of the amplifier circuit due to the influence of the burst noise,
Because it is configured to block by capacitance,
Noise can be removed without externally connecting a capacitor, which is advantageous in reducing the noise and cost of the circuit.

In the case of the semiconductor electret condenser microphone according to the sixth and seventh aspects of the present invention, since the above-described semiconductor amplifier circuit is used to amplify the audio signal, the above advantages of the same circuit can be similarly obtained. Therefore, it has great significance in reducing noise and cost.

[Brief description of the drawings]

FIG. 1 is a diagram for describing an embodiment of a semiconductor amplifier circuit of the present invention, and is a circuit diagram of the circuit.

FIG. 2 is a circuit diagram for explaining a modification of the circuit.

FIG. 3 is a view for explaining an embodiment of the semiconductor electret condenser microphone of the present invention, and is a schematic sectional view of the microphone.

FIG. 4 is a schematic exploded perspective view of a case of the microphone.

5A is a schematic sectional view of the case, and FIG. 5B is a schematic bottom view of the case.

FIG. 6 is a schematic plan view of a spacer layer of the microphone.

FIG. 7 is a schematic sectional view of a diaphragm of the microphone.

FIG. 8 is a circuit diagram showing an electrical connection relationship with a microphone in the circuit shown in FIG. 2;

FIG. 9 is a graph showing a relationship between a burst noise level and a frequency included in the audio signal output from the semiconductor amplifier circuit.

FIG. 10 is a diagram for explaining a conventional semiconductor electret condenser microphone, and is a schematic sectional view of the microphone.

FIG. 11 is a diagram for explaining a conventional semiconductor amplifier circuit, and is a circuit diagram of the same circuit.

[Explanation of symbols]

 Reference Signs List 10 voltage conversion circuit 20 amplifier circuit C semiconductor chip α audio signal β voltage signal γ audio signal

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiaki Obayashi 1-4-33 Kitakyuho-ji Temple, Yao City, Osaka Prefecture Inside Hoshiden Co., Ltd. (72) Inventor Mamoru Yasuda 1-4-33 Kitakyuhoji Temple, Yao City, Osaka Prefecture Inside Hosiden Co., Ltd. (72) Inventor Shinichi Saeki 1-4-3, Kitakyuhoji, Yao-shi, Osaka Prefecture Inside Hosiden Co., Ltd. (72) Inventor Shuji Osawa 1-4-33 Kitakyuhoji, Yao-shi, Osaka Ho-Siden F term in reference (reference) 5D021 CC03 CC15 5J092 AA02 AA11 CA41 CA91 HA01 HA25 KA64 QA03 QA04 SA13 TA01 UR14

Claims (7)

[Claims] In a semiconductor amplifier circuit for amplifying and outputting a small signal, a small signal is input, a voltage conversion circuit for outputting the signal as a voltage signal, and a voltage signal output from the voltage conversion circuit are input. And an amplifier circuit for amplifying and outputting the signal, wherein the voltage conversion circuit and the amplifier circuit are formed in the same semiconductor chip. 2. The semiconductor amplifier circuit according to claim 1, wherein said voltage conversion circuit is connected to a source, and said junction or MOS FE in which said small signal is input to a gate.
A semiconductor amplifier circuit comprising: T; and a resistor connected between a drain of the FET and a power supply line, for converting a drain current of the FET into a voltage and outputting the voltage as a voltage signal. 3. The semiconductor amplifying circuit according to claim 1, wherein said voltage conversion circuit comprises: a junction-type or MOS-type first FET to which said minute signal is input to a gate and grounded at a source; A second FET that has a source-drain connected between the drain and the power supply line of the first FET and outputs the source voltage as a voltage signal; F
A semiconductor amplifier circuit having a reference voltage generation circuit that outputs a signal to a gate of an ET. 4. The semiconductor amplifier circuit according to claim 1, wherein said amplifier circuit is provided with a gain adjustment circuit for enabling a gain of said circuit to be adjusted from outside. Semiconductor amplifier circuit. 5. The semiconductor amplifier circuit according to claim 1, wherein the output of the amplifier circuit is connected to a power supply line and / or
Alternatively, a semiconductor amplifier circuit provided with a surge protection capacitance formed by using a transistor between the semiconductor amplifier circuit and a ground line. 6. A capacitor is formed by the vibrating membrane and the back electrode, and a voice is converted into a voice signal by utilizing a change in capacitance of the capacitor due to vibration of the vibrating membrane, and the signal is amplified and output. In the semiconductor electret condenser microphone to amplify the audio signal,
A semiconductor electret condenser microphone using the semiconductor amplifier circuit according to claim 1, 2, 3, 4, or 5. 7. The semiconductor electret condenser microphone according to claim 6, wherein
Alternatively, a semiconductor electret condenser microphone, wherein an electrode layer serving as the back electrode is provided on an upper surface side of a semiconductor chip on which the semiconductor amplifier circuit according to 5 is formed.