
acoustic pressure signal p(t) to an output voltage v
R
(t). The movable membrane and fixed plate form
a capacitor. The sound waves deflect the membrane changing the separation between it and the back
plate and, therefore, the capacitance. A bias voltage is applied to produce an electrical charge on the
membrane. The motion of the membrane is opposed by damping and elastic forces as well as an
electrostatic force.
The mathematical model consists of the following different ial and algebraic equations describing
the circuit and the forces acting on the membrane:
R
dQ
dt
þ v
C
¼ E
0
, v
R
¼ E
0
v
C
(7:12)
Q ¼ Cv
C
(7:13)
C ¼
B
h
¼
B
L x
(7:14)
0 5 10 15 20 25 30 35 40 45 50