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Charge amplifiers transform charge output signals with high-impedance from the transducer to low-impedance voltage or current.
Structure
A charge amplifier operates similar to integrator. An opamp along with a feedback capacitor is used to construct charge amplifier. Since the transducer works like differentiator, the two-transfer functions cancel and the output voltage is proportional to the charge produced by the transducer. Since capacitance is always at a virtual earth.
, stray capacitance at the input to the amplifier does not effect the operation.
Applications
Charge amplifiers are low-cost devices that are used in the aerospace, medical, and industrial applications, and measurement of variables such as acceleration, force, temperature, and dynamic pressure. In addition, it is used for following purposes given below:
- Used for accelerometer signal conditioning
- Used with pressure transducers and high intensity microphones in vehicle dynamics studies
- Used for guitar pickup amplifiers
- Used for vibration transducers
- Used in pacemakers that include an accelerometer to detect motion
- Used for nuclear instrumentation
Precautions
Since extra charges can be produced by friction and lead to unwanted noise output,
cable from the transducer to the amplifier should not be subject to vibration.
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