Microphone assembly and method of reducing a temperature dependency of a microphone assembly
A microphone assembly and a method for reducing a temperature dependency of a microphone assembly are disclosed. In an embodiment, the microphone assembly includes a transducer and a voltage supply for the transducer, wherein the voltage supply is configured to supply a temperature dependent voltage for reducing a temperature dependency of the microphone assembly.
1. A microphone assembly comprising:
a transducer comprising a diaphragm and a back-plate; and
a voltage supply for supplying a bias voltage between the diaphragm and the back-plate of the transducer,
wherein the supplied bias voltage is a temperature dependent voltage for reducing a temperature dependency of a sensitivity of at least parts of the microphone assembly, and
wherein the supplied bias voltage changes with a temperature such that a change in a sensitivity of the parts is reduced as compared to a change in a sensitivity at a constant bias voltage.
2. The microphone assembly of claim 1 , wherein the supplied bias voltage changes with the temperature such that a change in an overall sensitivity of the microphone assembly is reduced.
3. The microphone assembly of claim 1 , wherein the supplied bias voltage changes with the temperature such that a change of a sensitivity of the transducer is reduced.
4. The microphone assembly of claim 1 , further comprising an amplifier for processing a signal of the transducer, wherein the supplied bias voltage changes with the temperature such that a change of a gain of the amplifier with the temperature is reduced.
5. The microphone assembly of claim 1 , wherein the voltage supply comprises a temperature dependent element for adjusting the supplied voltage as a function of the temperature.
6. The microphone assembly of claim 1 , wherein the voltage supply comprises a memory for enabling a calibration of the voltage supply such that the supplied bias voltage changes with the temperature.
7. The microphone assembly of claim 1 , wherein a temperature coefficient of the voltage supply matches a temperature coefficient of the transducer.
8. The microphone assembly of claim 7 , wherein the temperature coefficient of the voltage supply is opposite in sign to the temperature coefficient of the transducer.
9. The microphone assembly of claim 7 , wherein the temperature coefficient of the voltage supply is
TC
VS
≡
∂
V
bias
∂
T
=
-
1
k
SV
(
TC
mems
,
0
❘
d
B
+
∂
G
amp
❘
d
B
∂
T
)
wherein T is the temperature, V bias is a bias voltage supplied to the transducer, G amp|dB is a gain of an electronic circuit in logarithmic units, k SV is a slope factor of a sensitivity of the transducer versus V bias and TC mems,0|dB is the temperature coefficient of the transducer in logarithmic units at an operating voltage V 0 .
10. The microphone assembly of claim 7 , wherein the temperature coefficient of the voltage supply is
TC
VS
≡
∂
V
bias
∂
T
=
-
TC
mems
,
0
❘
d
B
k
SV
wherein T is the temperature, V bias is a bias voltage supplied to the transducer, k SV is a slope factor of a sensitivity of the transducer versus V bias and TC mems,0|dB is the temperature coefficient of the transducer in logarithmic units.
11. A method of reducing a temperature dependency of a microphone assembly, the method comprising:
providing a transducer and determining a temperature dependency of the transducer including a temperature coefficient;
providing a voltage supply for supplying a bias voltage between a diaphragm and a back-plate of the transducer, wherein the voltage supply enables supplying a temperature dependent voltage for compensating a temperature dependency of the transducer;
determining a temperature coefficient of the voltage supply; and
assembling the transducer with the voltage supply, wherein the transducer is only assembled with the voltage supply if the temperature coefficient of the voltage supply matches the temperature coefficient of the transducer.
12. A method of reducing a temperature dependency of a microphone assembly, the method comprising:
providing a transducer;
providing a voltage supply for supplying a bias voltage between a diaphragm and a back-plate of the transducer; and
assembling the transducer with the voltage supply,
wherein, after assembling, the voltage supply is calibrated such that a temperature coefficient of the voltage supply matches a temperature coefficient of the transducer.
13. The method of claim 12 , wherein a calibration involves calculating a slope factor of a sensitivity of the transducer versus the voltage supplied by the voltage supply.
14. The method of claim 12 , wherein a calibration involves measuring a sensitivity of the microphone assembly.