Phase Delay and Filter Lag Introduced by Capacitive Pressure Transducer Retrofits
Retrofitting capacitive pressure transducers introduces hydraulic dead-volume delay and digital ASIC filter lag that erodes control loop phase margin.
Switched-Capacitor Circuit
Electrical Network
Electronic circuits that emulate resistors using a combination of capacitors and periodically operated switches perform critical functions in analog signal processing. Integrating a switched-capacitor circuit allows for the precise implementation of filters, amplifiers, modulators and analog-to-digital converters on a single silicon chip. This approach replaces physical resistors, which are difficult to manufacture with high precision, with more accurate capacitor ratios.
Charge Transfer
Non-overlapping clock signals control the open and closed states of the switches to move charge from one capacitor to another. This charge movement occurs in discrete time steps and simulates the continuous flow of current through a resistor.
Signal Processing
High-precision filtering of analog signals is achieved by adjusting the switching frequency, which directly controls the equivalent resistance of the network. This capability allows the filter’s cutoff frequency to be tuned electronically across a wide range.
Design Advantage
Monolithic integrated circuits benefit from this technique because capacitors occupy less silicon area and can be matched with a high degree of precision compared to high-value resistors. Temperature drift is minimized because the performance of the network depends on the ratio of the capacitances rather than their absolute values. This ratiometric property ensures stable operation of the signal conditioning circuitry over a wide temperature range and throughout the operating lifetime of the sensor.