Signal Chain Reconfiguration for Capacitive and Piezoresistive Transducer Alternates
Reconfiguring signal chains between capacitive and piezoresistive transducers requires matching input impedance, excitation sources, and thermal compensation math.
Instrumentation Amplifier
Precision Amplifier
Specialized differential gain blocks configured with high input impedance and precise closed-loop gain amplify weak sensor signals amidst significant common-mode noise. A standard instrumentation amplifier utilizes three operational amplifiers configured to decouple input impedance matching from common-mode rejection performance. Measurement validity stops when common-mode voltage exceeds supply rail boundaries.
Common Mode Rejection
Symmetric input stages process differential sensor signals while suppressing identical voltage offsets present on both input leads. Laser-trimmed internal resistor networks ensure tight matching required for high common-mode rejection ratios across operating frequencies. Input bias currents flowing through source impedance mismatches generate differential error voltages that bypass common-mode rejection mechanisms.
Differential Gain
Single resistor configuration sets the overall differential voltage gain without degrading common-mode rejection ratio performance. Input buffer stages provide gigohm source impedance to prevent sensor loading errors. Output amplifier stages convert buffered differential signals into single-ended output voltages referenced to a ground pin.
Thermal drift in gain-setting resistors changes differential amplification factors over ambient temperature cycles. Frequency response decreases predictably as set gain increases due to fixed gain-bandwidth product limits. Gain accuracy depends on internal resistor matching stability over operating lifespans.
Metrological Test
Automated test stations measure common-mode rejection, offset voltage, and gain error using precision voltage calibrators. Calibration certificates report operational specifications verified at standard reference supply voltages.