Optimal design of an electret microphone metal-oxide-semiconductor field-effect transistor preamplifier

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

doi:10.1121/1.403660

Cited by 10 publications

(3 citation statements)

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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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“…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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“…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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“…Today's microphones are of four types: dynamic, condenser, condenser -electret, and piezoelectric. Most previous micromachined microphone work [1][2][3][4][5][6][7][8][9][10][11][12][13][14] has focused on condenser microphones because of their high sensitivity, simplicity, potential for miniaturization, and compatibility with thin film fabrication techniques.…”

Section: Introductionmentioning

confidence: 99%

A Micromachined Silicon Condenser Microphone with On-Chip Amplifier

Bernstein¹,

Borenstein²

1996

1996 Solid-State, Actuators, and Microsystems Workshop Technical Digest

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Monolithic silicon microphones have been fabricated which include on-chip JFET buffer amplifiers, providing a complete microphone plus electronics on a single silicon chip. Test data is presented showing sensitivities as high as 40 mV/Pa (-48 dB ref. lV/µBar), with routine sensitivity of 15 mV/Pa (-57 dB ref. lV/µBar) and bandwidth of 70 Hz to 20 kHz.Noise measurements show that electronics noise from the gate bias resistor is dominant, leading to ltf 2 noise spectral density.The fabrication of these microphones uses both surface and bulk micromachining (Fig. 1). Surface micromachining (precision electroforming) is used to make the perforated bridge electrodes, while bulk micromachining is used to form the diaphragm and through-hole. Diaphragms of p + doped silicon from I to 2 mm in diameter have been tested. A monolithic ion implanted JFET and polysilicon resistors are fabricated on-chip.An analysis of the theoretical attainable sensitivity of a micromachined condenser microphone will be presented. A theoretical Figure of Merit proportional to the microphone signal to noise ratio is derived, which allows the microphone design to be optimized. M =(8• V Bias •xf J • ( l+� J -I •[l+s_ ) -I 27 • co • V c CcA v CGap

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Optimal design of an electret microphone metal-oxide-semiconductor field-effect transistor preamplifier

Cited by 10 publications

References 0 publications

Feasibility study of a MEMS microphone design using the PolyMUMPs process

Feasibility study of a MEMS microphone design using the PolyMUMPs process

Design and analysis of diaphragms in dynamic microphones

A Micromachined Silicon Condenser Microphone with On-Chip Amplifier

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