General considerations of noise in microphone preamplifiers

Donk, A.G.H. van der; Voorthuyzen, J.A.; Bergveld, Piet

doi:10.1016/0924-4247(91)87042-2

Cited by 11 publications

(4 citation statements)

References 3 publications

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“…The electrtcal open-crrcmt sensrtrvrty mcreases with mcreasmg static centre deflection Consequently, the maxrmum possible total sensrtrvrty can be obtained by takmg the hrghest possible bras voltage V, resultmg m a maxrmum deflection of the diaphragm If the value of the input capacrtance of the amplifier 1s infinite, which occurs tf a charge amplifier is used, the value of the sensrtmrty theoretically also becomes mfimte However, m this srtuatron a small sound pressure mrght already cause a collapse of the diaphragm Therefore, the maxnnurn rrncrophone sensrtrvrty and the maxnnum deflection are hmrted by a maxmmm allowable sound pressure that has to be specrfied Higher pressures will cause a collapse of the diaphragm If both thrs maxnnum allowable sound pressure and the consrderatrons concemmg noise performance of condenser microphones with a preampuer [26,27] are taken into account, rt IS possible to optrmrze the overall performance of a condenser nncrophone wrth a preamplmer Experrments carried out to analyse the mechanical sensmvrty and the total sensttrvtty show a good agreement between the model of rmcrophones with a hrghly tensioned diaphragm and the measurement results…”

Section: Methodsmentioning

confidence: 99%

“…Nevertheless, it wdl be shown m Section 7 that the use of a charge amptier does not automatically result m the optunal overall performance of the microphone, although the total sensltlvlty 1s higher than when a voltage amphfier 1s used 42 Mechanrcal sensttw@ of the mmvphone with a draphragm muth a large m&al stress By using eqns (21) and (26), eqn (27) becomes, for diaphragms with a large mltlal stress, As m Sectlon 4 1, it can be derwed for diaphragms unth a large untlal stress, wbch have a quadratic curvature according to eqn (.5), that [20] where V has to be replaced by the right--hand part of eqn (25) The mechanical sensltlvlty can be calculated by using eqn (33) wth the substltutlon of eqns (34) and (35) Agam, the expression for the mechanical sensltnrlty IS not shown m this Se&on because of tts complex@ By dIvldmg the mechantcal sensitivity by sJud, the expression for the senslttwty changes mto a dlmenslonless shape to that mentioned at the end of Section 3 2 the mechanical sensltmty of microphones wtth a dtaphragm with a large mltlal stress (membrane) 1s about 1000 tunes smaller than the sensltlvlty of the same rmcrophones Hrlth a stress-free dtaphragm (thm plate)…”

Section: (Wmentioning

confidence: 99%

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Modelling of silicon condenser microphones

Donk

Scheeper

Olthuis

et al. 1994

Sensors and Actuators A: Physical

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Several models concemmg the senslhvlty of capaclhve pressure sensors have been presented m the past Modellmg of condenser nucrophones, which can be constdered to be a specml type of capacltlve pressure sensor, usually reqmres a more comphcated analysis of the senstttvlly, because they have a strong electnc field m the atr gap It IS found that tbe mechamcal sensltlvlty of condenser rmcrophones ~nth a ctrcular diaphragm, either mth a large uutlal tenston or without any mltml tensloo, Increases mth mcreasmg bias voltage (and the correspondmg static deflection), whereas the mechamcal sensltrvlty of other capacltrve pressure sensors does not depend on the static deflection It is also found that the mechamcal senslttv@ increases wtth mcreasmg input capacitance of a preamphfier In addltlon, the open-clrcmt electrical sensltlvlty and, consequently, the total sensltlvlty too, also Increases mth mcreasmg bras voltage (or stahc deflechon) However, the maxtmum allowable sound pressure at which the diaphragm collapses, an effect that has to be taken into account, decreases Hrlth mcreasmg static deflection in most cases, uhnnately resulting in an optimum value for the bias voltage The model for microphones with a nrcular highly tensloned diaphragm has been venfied successfully for two mlcrophone types *Present address Texas Instruments

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Section: Methodsmentioning

confidence: 99%

Section: (Wmentioning

confidence: 99%

Modelling of silicon condenser microphones

Donk

Scheeper

Olthuis

et al. 1994

Sensors and Actuators A: Physical

Self Cite

View full text Add to dashboard Cite

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“…The main noise contributors are the pre-amplifier and the biasing resistor [6][7][8]. The 1/f (flicker) noise has an inverse dependency on the transistor area [9].…”

Section: (Oise Considerationsmentioning

confidence: 99%

Feasibility study of a MEMS microphone design using the PolyMUMPs process

Grixti

Grech

Casha

et al. 2014

2014 Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS (DTIP)

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The scope of this paper is to underline the design issues of MEMS microphones and presents a test case designed using the PolyMUMPs process with an additional back-etch processing step. Both circular and square (simply supported and clamped) diaphragm designs are considered. The effect of the back chamber volume on the microphone sensitivity is also investigated. The finalized design is based on the clamped square diaphragm with a bottom sound port. The bias voltage is 6 V and the diaphragm has a side-length of 675 µm. The back-plate includes several holes which amount to a perforation ratio of 0.33. The maximum allowable input pressure before pull-in is 139 dB SPL. The microphone with a back-chamber volume of 6 mm 3 has a sensitivity of 8.4 mV/Pa at 94 dB SPL at 1 kHz. The complete package size with the ASIC included is targeted to be 3x2.5x1 mm, assuming that the ASIC is of a comparable size to that of the MEMS sensor.

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“…Numerous microphone technologies were gradually developed, including ribbon and dynamic microphones and the applied condenser and electret microphones, the last two of which remain widely available. [3][4][5][6][7][8][9][10][11][12] Microphones collect sound in the recording link. In the earliest mechanical recorder, the microphone converted acoustic signals into diaphragm vibrations; these vibrations were then transmitted to a stylus and recorded in a series of indentations on a piece of tinfoil.…”

Section: Introductionmentioning

confidence: 99%

Design and analysis of diaphragms in dynamic microphones

Huang

Shiu

2015

Advances in Mechanical Engineering

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Most contemporary high-end microphones are dynamic microphones, adopting the most basic electromagnetic transduction principles. This study investigated the diaphragm structures of dynamic microphones. The diaphragms were composed of polyimide material, and the boundary settings required for actual operation were provided using finite element model analysis software. The characteristic frequencies caused by grooving variations on the three-dimensional diaphragm were analyzed for the various groove shapes and number. The groove angles and width variations were examined based on the optimal groove shape selected in the aforementioned analysis, and the effects of these shapes were determined based on the analytical results. Acoustic waves cause thin films to vibrate, forming the working principle behind dynamic microphones. The thin film drives a coil to vibrate in a magnetic field and cuts the line of magnetic force, subsequently producing a voltage on both ends of the coil. This audio-frequency-inducted voltage represents an acoustic wave message. The finite element model analysis software was used to conduct electromagnetic induction simulations; the sound source was fed to the diaphragm to drive the coil. The coil vibrations caused the line of magnetic force to be cut, and the final voltages produced were examined and compared.

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General considerations of noise in microphone preamplifiers

Cited by 11 publications

References 3 publications

Modelling of silicon condenser microphones

Modelling of silicon condenser microphones

Feasibility study of a MEMS microphone design using the PolyMUMPs process

Design and analysis of diaphragms in dynamic microphones

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