
91-21Ampliers and Signal Conditioners
91.7 Carrier Ampliers
A carrier amplier is a conditioner for extremely narrowband ac signals from ac-driven sensors. A car-
rier
amplier is made of a sine wave oscillator, to excite the sensor (either directly as in LVDTs, or placed
in a voltage divider or sensor bridge, as in sensors based in a variable capacitance, inductance, or resis-
tance),
an ac voltage amplier for the sensor output, a synchronous demodulator, and a low-pass lter
(Figure 91.15). e AD598, AD698, and NE5520/1 are carrier ampliers in IC form intended for (but not
limited to) LVDTs driven at a frequency from 2 to 20 kHz.
Carrier ...