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ADPD2210ACPZ-RL 数据表(PDF) 11 Page - Analog Devices |
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ADPD2210ACPZ-RL 数据表(HTML) 11 Page - Analog Devices |
11 / 16 page ADPD2210 Data Sheet Rev. A | Page 10 of 15 TERMINOLOGY Amperometry Amperometry is a technique used in chemistry and biochemis- try to detect ions in a solution by measuring very small currents between polarized electrodes. Methods of amperometry include direct, pulsed, and amperometric titration, where a substance (titrate) known to react with the analyte (the substance being measured) is added in measured quantities and the effect on the ionic concentration of the analyte is measured. Dark Current Dark current is the current flowing in a photodiode with no light incident upon the diode junction. In reversed bias operation, the dominant source of dark current is current generated by the bias voltage across the bulk resistance of the semiconductor material (shunt resistance). In zero bias operation, thermal generation of charge carriers in the depletion region becomes the dominant source of dark current. Linearity Linearity is a measure of the deviation from an ideal change in output current relative to a change in input current. Linearity is specified as the deviation from a best straight line fit of the amplifier current output over a specified range of input current. Linearity is a critical specification in photoplethysmography due to the requirement of sensing small ac signals impressed upon large dc offsets. Noise Equivalent Power (NEP) Noise equivalent power is the amount of incident light power on a photo detector, which generates a photocurrent equal to the total noise current of the sensor, expressed as A/√Hz. The NEP is the fundamental baseline of the detectivity of the optical sensor. Offset Offset in the ADPD2210 is defined as the differential voltage between the reference output and the input of the ADPD2210. The ADPD2210 holds the input terminal voltage to within ±5 mV (typical) of the reference terminal. Photoconductive Mode Photoconductive operation of a photodiode occurs when photons entering the silicon generate electron/hole pairs that are swept by the electric field to the opposite terminal. These carriers are presented at the terminals of the photodiode as a current proportional to the luminous flux incident on the junction of the photodiode. Photoplethysmography Photoplethysmography uses light to measure biological functions by sensing changes in the absorption spectra of soft tissue caused by differences in hemoglobin volume and composition. Common applications of photoplethysmography include transmission SpO2 pulse oximetry and reflectance HRM. Shot Noise Shot noise is a statistical fluctuation in any quantized signal such as photons of light and electrons in current. The magni- tude of the shot noise is expressed as a root mean square (rms) noise current. Shot noise is a fundamental limitation in photo detectors and takes the form of Shot noise = √(2qIPDBW) where: q is the charge of an electron (1.602 × 10−19 Coulomb). IPD is the photodiode current. BW is the bandwidth. Static Bias The ADPD2210 has an internal 10 nA bias that is used to linearize the input current mirror at low input levels and prevents transient reverse bias of the amplifier input stage. This bias is fixed and appears on the output as a 240 nA typical offset. Thermal (Johnson) Noise All resistors generate a noise component based on temperature, including the shunt resistance in a photodiode due to genera- tion of carriers within the bulk semiconductor. The magnitude of this generated noise current is calculated as follows: Photodiode Thermal Noise Current = RSH f kT 4 where: k = 1.38 × 10−23 joules per °K. k is the Boltzmann constant. T is the absolute temperature in degrees Kelvin (273 K = 0°C). Δf is the noise measurement bandwidth. RSH is the shunt resistance of the photodiode Thermal noise generated in the bulk semiconductor outside the depletion region of the photodiode appears as a broadband ac signal. Thermal noise generated within the depletion region appears as a dc current but is typically an insignificant compo- nent of dark current relative to the bias/shunt resistance component. |
类似零件编号 - ADPD2210ACPZ-RL |
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类似说明 - ADPD2210ACPZ-RL |
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