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JP2003032796

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2003032796
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
condenser microphone suitable for use in mobile phones and the like.
[0002]
2. Description of the Related Art Condenser microphones have been used as microphones for
mobile phones. FIG. 2 is a circuit diagram showing an electrical configuration of a conventional
condenser microphone. In FIG. 2, 1 is a field effect transistor (FET) for voltage-current
conversion, and 2 is a capacitor. The capacitor 2 is connected between the source and the gate of
the FET 1. Further, the drain of the FET 1 is connected to the power supply terminal 5 through
the external resistor 4 for voltage division. Further, an output terminal 3 is connected between
the external resistor 4 and the drain of the FET 1.
[0003]
The capacitor 2 is, for example, a synthetic resin film made of PPS (polyphenylene sulfide) having
a thickness of 2 μm, in which a charge is injected into a diaphragm (vibrating film) formed by
depositing a conductive metal film such as gold. For example, it is configured by sealing with a
conductive case (constituting a back electrode of a capacitor) made of a material such as stainless
steel, aluminum, or a conductive plastic. When the user utters an audio, the diaphragm vibrates
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due to the sound wave, and the gap (distance) between the thin film of the diaphragm and the
conductive case (back electrode) fluctuates, and the terminal between the two terminals of the
capacitor 2 The potential difference changes. Since the voltage due to the change in the potential
difference between the two terminals is applied to the gate of the FET 1, a current corresponding
to the change in the potential difference is output to the output terminal 3, whereby the user's
voice is an electric signal It is obtained as (current).
[0004]
Generally, in the manufacture of a condenser microphone, the size of the gap between the
diaphragm (diaphragm) and the case (back electrode), the amount of static electricity to be
applied to the diaphragm, etc. Because of the presence of variations, the output current (output
sensitivity) output from the FET 1 also has variations. Therefore, when manufacturing a
condenser microphone, a current of a constant value is supplied from the power supply terminal
5 to the FET 1 at the final stage of manufacture to measure the value of the current output to the
output terminal 3 side. The output sensitivity is checked, and those out of the appropriate range
are selected as defective. For those selected as defective products, theoretically, methods such as
adjusting the gap between the vibrating membrane and the case (back electrode), adjusting the
charge amount of the vibrating membrane, and exchanging the external resistance in FIG.
Although it is conceivable to correct the output sensitivity by using this method, it is extremely
difficult to adjust the sensitivity in this way in practice (for example, in the circuit of FIG. It is
extremely difficult in practice to replace the external resistor 4 to adjust the sensitivity, etc.).
Therefore, the condenser microphones classified as defective products are disassembled, some
reusable parts such as circuit boards are reused, and other parts (the case, diaphragm, etc.) are
discarded. .
[0005]
In the conventional condenser microphone as described above, as described above, it is difficult
to adjust the value of the current supplied from the power supply terminal 5 to the FET 1 in the
inspection process of the output sensitivity in the final stage of manufacture. There is a problem
that complicated operations are required to adjust the supply current when performing highaccuracy inspection. Further, in the conventional condenser microphone as described above, the
amount of consumption current supplied from the power supply terminal 5 to the FET 1 varies
depending on the state of charge of the battery or the like during use by the user. There was a
problem that energy loss occurred at the time.
04-05-2019
2
[0006]
Further, in the conventional condenser microphone as described above, when the sensitivity is
out of the proper range in the inspection process of the output sensitivity, all are disassembled as
defective products as described above (after production) However, with this method, the product
yield remains low (for example, about 60 to 70%), and there is a problem that a large number of
parts that can not be reused but are discarded are generated. The
[0007]
The present invention has been made focusing on the problems of the prior art as described
above, and simplifies the adjustment of the current flowing from the power supply terminal in
the inspection process of the output sensitivity in the final stage of manufacturing of the
condenser microphone. It is possible to provide a condenser microphone which can realize the
low power consumption at the time of use by making the inspection process efficient and making
the current supplied to the FET 1 constant regardless of the battery charge condition etc. To aim.
Another object of the present invention is to provide a condenser microphone capable of greatly
improving the yield of products by enabling the output sensitivity to be easily corrected after
manufacture.
[0008]
SUMMARY OF THE INVENTION A condenser microphone according to the present invention for
solving the problems of the prior art as described above emits a user by providing a diaphragm
or a diaphragm that vibrates by the sound emitted by the user. A capacitor configured such that a
potential difference between both terminals changes according to voice, a source and a gate are
connected to each other via the capacitor, and a drain is connected to the output terminal side. A
transistor and a second field effect transistor having a source connected to the output terminal
side, a source and a gate connected to each other, and a drain connected to the power supply
terminal side. It is.
[0009]
Further, the condenser microphone of the present invention is provided with a diaphragm or a
diaphragm which is vibrated by the voice emitted by the user, so that the capacitor configured to
change the potential difference between the two terminals according to the voice emitted by the
user. A source and a gate are connected to each other via the capacitor, and a drain is connected
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3
to the output terminal side, a source is connected to the output terminal side, and the source and
the gate are connected And a second field effect transistor whose drain is connected to the power
supply terminal side, and a sensitivity adjusting resistor connected between the source and the
gate of the second field effect transistor. It is a feature.
[0010]
Preferably, in the condenser microphone of the present invention, the sensitivity adjusting
resistor is a variable resistor.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below.
FIGS. 1 (a) and 1 (b) are circuit diagrams showing the electrical configuration of the condenser
microphone according to the present embodiment.
In FIG. 1, reference numeral 1 denotes a field effect transistor (FET) in which a capacitor 2 is
connected between a source and a gate, and a drain is connected to the output terminal 3 side.
The capacitor 2 may be, for example, stainless steel in which a charge is injected into a
diaphragm (vibrating film) formed by depositing a conductive metal film such as gold on a
synthetic resin film made of PPS (polyphenylene sulfide) having a thickness of 2 μm. It is
configured by sealing with a conductive case (constituting a back electrode of a capacitor) made
of a material such as aluminum or conductive plastic. When the user utters a voice, the
diaphragm vibrates due to the sound wave, and the gap (distance) between the thin film of the
diaphragm and the conductive case (back electrode) fluctuates. The potential difference of Since
the voltage due to the change in the potential difference between the two terminals is applied to
the gate of the FET 1, a current corresponding to the change in the potential difference is output
to the output terminal 3, whereby the user's voice is an electric signal It is obtained as (current).
[0012]
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4
Further, in FIG. 1, reference numeral 11 denotes a field effect transistor (FET) having a source
connected to the side of the output terminal 3 and a drain connected to the side of the power
supply terminal 5 for supplying a current. Further, in FIG. 1, reference numeral 12 denotes a
variable resistor for sensitivity adjustment connected between the source and the gate of the FET
11.
[0013]
In the circuit of this embodiment shown in FIG. 1, since the FET 11 is connected between the
gate and the source, the value of the current supplied from the power supply terminal 5 is always
kept constant. Constitute a constant current circuit for supplying Therefore, in the present
embodiment, the constant current circuit configured by the FET 11 even if the value of the
current for inspection from the power supply terminal 5 slightly fluctuates in the inspection
process of the output sensitivity in the final stage of manufacturing the capacitor microphone.
Thus, a current of a constant value is always supplied to the FET 1 so that highly accurate
inspection is possible. Therefore, in the present embodiment, it is not necessary to perform
complicated adjustment to set the current supplied from the power supply terminal 5 to the FET
1 to a constant value in the inspection step as in the conventional case, and the inspection step is
greatly simplified. Will be Further, in the present embodiment, the presence of the constant
current circuit using the FET 11 prevents the current value supplied from the power supply
terminal 5 to the FET 1 from fluctuating due to the charge condition of the battery as in the prior
art. Since a constant current is supplied to the FET 1, the FET 1 can be prevented from being
supplied with an excessive current more than necessary, and power consumption can be reduced
during use.
[0014]
Further, in the circuit of this embodiment shown in FIG. 1, the sensitivity adjusting variable
resistor 12 is connected between the source and the gate of the FET 11. Therefore, in the present
embodiment, the current supplied to the FET 1 can be changed by changing the resistance value
of the variable resistor 12. As a result, the current value output from the FET 1 to the output
terminal 3 side can be changed. The range, that is, the output sensitivity can be easily adjusted.
Therefore, in the present embodiment, the output sensitivity is adjusted and corrected extremely
easily by changing the resistance value of the variable resistor 12 even for those whose
sensitivity is selected as inappropriate in the inspection step in the final stage of production. be
able to. Therefore, according to the present embodiment, the manufacturing yield of the
capacitor microphone can be greatly improved, and the manufacturing cost of the capacitor
04-05-2019
5
microphone can be significantly reduced.
[0015]
According to the experiment of the inventor of the present invention, even if the output terminal
3 is connected to the position indicated by reference numeral 3a in FIG. 1 (a) in the circuit of FIG.
Even when connected to the position shown by 3b, the same signal was obtained in any case.
[0016]
In the embodiment described above, a variable resistor (including a digital variable resistor) 12 is
used as a sensitivity adjusting resistor connected between the source and the gate of the FET 11.
However, the present invention is not limited to this, and a fixed resistor may be used instead of
the variable resistor 12.
Even in the case of using a fixed resistor, it is possible to easily adjust and correct the output
sensitivity of the capacitor microphone by replacing with a fixed resistor having another
resistance value after manufacturing the capacitor microphone.
[0017]
In the present invention, as in the present embodiment, the sensitivity adjustment resistor is not
connected between the source and the gate of the FET 11 (the resistance value of the sensitivity
adjustment resistor 12 is zero). Is also possible. In this case, the output sensitivity can not be
adjusted by the sensitivity adjustment resistor, but even in this case, the operation of the
constant current circuit using the FET 11 simplifies the current supply operation in the
inspection process ( In the inspection step, the complicated operation for making the value of the
current supplied from the power supply terminal 5 to the FET 1 constant is not required), and
the power consumption at the time of use is reduced (the current supplied to the FET 1 is It is
possible to make it a constant value to avoid supplying an unnecessary excessive current).
[0018]
When manufacturing the condenser microphone of the present invention, for example, two
identical FETs connected in series are made into an IC package in advance and connected to the
condenser 2 of FIG. If the adjustment resistor 12 is externally attached to the circuit (or the
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resistance is previously formed in the circuit and the resistance value is adjusted later using a
laser beam etc.), low cost and efficient manufacture Is desirable and desirable.
[0019]
As described above, in the present invention, between the first field effect transistor for
converting the voltage from the capacitor to the current and the power supply terminal, the gate
and the source are connected. The second field effect transistors connected to each other are
connected.
Therefore, in the present invention, the current supplied from the power supply terminal is
always kept at a constant value by the second field effect transistor and supplied to the first field
effect transistor. Therefore, according to the present invention, in the inspection process of the
output sensitivity in the final stage of the manufacturing of the condenser microphone, even if
the current value from the power supply terminal fluctuates to some extent, the second field
effect transistor (constant current circuit) Since a constant current is always supplied to the first
field effect transistor, it is not necessary to perform complicated adjustment to set the current
supplied from the power supply terminal to a constant value in the inspection process as in the
prior art. The inspection process will be greatly simplified.
[0020]
Further, according to the present invention, the presence of the second field effect transistor
(constant current circuit) makes it possible to use the power supply terminal from the power
supply terminal according to the charging condition of the battery as in the prior art when using
a mobile phone or the like. It is prevented that the value of the current supplied to the first field
effect transistor fluctuates, and a constant current is always supplied to the first field effect
transistor. Excessive current more than necessary is prevented from being supplied, and power
consumption at the time of use is reduced.
[0021]
Furthermore, in the present invention, since the sensitivity adjustment resistor is connected
between the source and the gate of the second field effect transistor, the resistance adjustment
resistor may be changed by changing the resistance value of the sensitivity adjustment resistor.
The current supplied to the first field effect transistor can be easily changed, and the magnitude
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(output sensitivity) of the output current output from the first field effect transistor to the output
terminal can be easily adjusted. it can.
Therefore, according to the present invention, the resistance adjustment resistor is changed in
resistance value (in the case of variable resistance) or for the sensitivity adjustment even for
those whose output sensitivity is classified as poor in the inspection step in the final stage of
production. The output sensitivity can be adjusted and corrected extremely easily by a method
such as exchanging resistance with other resistance values (in the case of fixed resistance) or the
like. Therefore, according to the present invention, the manufacturing yield of the condenser
microphone can be improved, and the manufacturing cost can be significantly reduced.
[0022]
Brief description of the drawings
[0023]
1 is a circuit diagram showing an electrical configuration of a condenser microphone according
to an embodiment of the present invention.
[0024]
FIG. 2 is a circuit diagram showing an electrical configuration of a conventional condenser
microphone.
[0025]
Explanation of sign
[0026]
1 11 field effect transistor 2 capacitor 3 output terminal 4 external resistor 5 power supply
terminal 12 variable resistance for sensitivity adjustment
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