Sources of excess noise in silicon piezoresistive microphonesa)
Piezoresistors configured in Wheatstone bridge.
(Color online) (a) Top view and (b) cross section of a piezoresistive microphone (Ref. 3).
(a) Lumped element model of a piezoresistive microphone, (b) noise equivalent circuit of a piezoresistive microphone.
(Color online) Experimental setup of the noise measurement.
Small signal representation of the setup with a metal film resistor.
Voltage noise PSD of a metal film resistor without and with the subtraction of the equipment setup noise.
(Color online) Experimental setup for an ac bridge measurement.
(a) Power spectral density of UF piezoresistive microphone at zero bias voltage, (b) power spectral density of UF piezoresistive microphone at different bias voltages, (c) power spectral density of UF proximity sensor at different bias voltage (constant reverse bias of ), and (d) power spectral density of Endevco microphone (Model 8510B-1) at different bias voltage.
Power spectral density of Kulite microphone (MIC-093) at different bias voltage compared to the dc setup noise.
(a) Power spectral density of the Bruel and Kjaer 4138 condenser microphone and of the UF piezoresistive microphone and (b) coherence function between the B&K 4138 and UF piezoresistive microphone.
Power spectral densities of noise sources due to the damping resistance, the radiation resistance, and the vent resistance.
Power spectral densities comparison of total thermomechanical noise to setup noise, electrical thermal noise, and electrical noise.
(Color online) (a) Power spectral density of the UF piezoresistive proximity sensor with free diaphragm and (b) power spectral density of the UF piezoresistive proximity sensor with fixed diaphragm.
Lumped element parameters of piezoresistive microphone (Ref. 26) computed for UF microphone (Ref. 3).
Measured input and output impedances and overall sensitivity of UF1 piezoresistive microphone, UF2 piezoresistive proximity sensor, and Kulite and Endevco piezoresistive microphones.
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