Modelling of silicon condenser microphones

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