Internal Reference Voltage Droop under External Analog Loading
External analog load currents extract direct current and charge pulses from internal bandgap reference nodes, inducing static droop and transient conversion errors.
Sample and Hold
Electronic Synchronization
An analog circuit component freezes a continuous input signal at a precise moment to present a static voltage for downstream processing. The sample and hold device maintains this discrete level during the time required for a subsequent analog to digital converter to complete a measurement cycle. Its primary operation requires a fast input buffer connected to a storage capacitor through an electronic switch.
When the switch closes, the capacitor tracks the input voltage until the switch opens again to retain the charge.
Control Timing
Logic signals govern the transition between the track mode and the hold mode. Jitter within the control clock introduces uncertainty in the exact instant of measurement which translates into amplitude errors for high frequency signals. Aperture delay defines the interval between the hold command and the actual physical opening of the internal switch.
Engineers specify this parameter to ensure the circuit captures the intended value before the input signal fluctuates beyond the allowed error budget.
Performance Limitation
Parasitic leakage through the switch resistance causes the stored voltage to droop over the duration of the conversion period. High temperature environments accelerate this charge dissipation and force a selection of components with low dielectric absorption. Designers choose high impedance input amplifiers to minimize current drain from the capacitor while in the hold state.
Measurement Integrity
Feedthrough occurs when the input signal capacitively couples to the output even while the circuit remains in the hold state. This interference creates a permanent offset error in the conversion result if the switch isolation impedance is insufficient. Proper circuit layout keeps these leakage paths to a minimum to ensure the captured sample represents the input signal within the rated tolerance.