Signal path of less impedance5/25/2023 Signals are processed by differential amplifiers throughout most of the circuit to minimize common mode effects and noise. The signal conditioning IC converts the differential signal from the sensor element (nominally ± 5 mV) into a single-ended signal in the 0.5–4.5 V range while correcting for the temperature-related signal variations. The data used to set the performance of the accelerometer is stored in fused registers within the signal conditioning IC. As a result, the output signal is accurate and no trimming is required by the user. The signal conditioning circuitry amplifies the output of the sensor element and corrects the sensitivity and offset changes that occur with overheating. Nihal Kularatna, in Modern Component Families and Circuit Block Design, 2000 7.6.2.1.2 Signal Conditioning Skepticism, tempered by enlightenment, is a useful tool when constructing a signal path and no amount of hope is as effective as preparation and directed experimentation. The preceding emphasizes vigilance in designing and maintaining a signal path. High quality signal pick-offs always specify insertion loss, corruption factors and probe output scale factor. In practice, some amount of disturbance must be tolerated and its effect on measurement results evaluated. Inserting the probe into the signal path necessitates some form of signal pick-off which nominally does not influence signal transmission. 1 Any such probe must be carefully frequency compensated before use or misrepresented measurement will result. Passive Z 0 types, commercially available in 500Ω (10×) and 5kΩ (100×) impedances, have input capacitance below 1pf. If probes must be used, their introduction to the signal path mandates attention to their connection mechanism and high frequency compensation. Similarly, oscilloscope connections should be made directly to the instrument’s 50Ω inputs, avoiding probes. Adapters introduce significant parasitics, resulting in reflections, rise time degradation, resonances and other degrading behavior. Mixing signal path hardware types via adapters (e.g. Optimal connection practice eliminates any cable by coupling the signal output directly to the measurement input. Additionally, cable should be 50Ω “hard line” or, at least, Teflon-based coaxial cable fully specified for high frequency operation. SMA components are preferred for the rise times described in the text. Familiar BNC hardware becomes lossy at rise times much faster than 350ps. Any form of connector, cable, attenuator or probe must be fully specified for high frequency use. Accordingly, introduction of elements or connections to the signal path should be minimized and necessary connections and elements must be high grade components. The practical result of such introduced aberrations is degradation of pulse rise time, fidelity, or both. The degree of signal corruption contributed by a given element varies with its deviation from the transmission lines nominal impedance. Connections, cables, adapters, attenuators and probes represent discontinuities in this transmission line, deleteriously affecting its ability to faithfully transmit desired signal. Subnanosecond rise time signal paths must be considered as a transmission line. Jim Williams, in Analog Circuit Design, 2013 Appendix E Connections, cables, adapters, attenuators, probes and picoseconds 2 nanosecond, 0.1% resolution settling time measurement for wideband amplifiers
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