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OPT301M bảng dữ liệu(PDF) 7 Page - Burr-Brown (TI) |
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OPT301M bảng dữ liệu(HTML) 7 Page - Burr-Brown (TI) |
7 / 11 page 6 7 ® OPT301 APPLICATIONS INFORMATION Figure 1 shows the basic connections required to operate the OPT301. Applications with high-impedance power supplies may require decoupling capacitors located close to the device pins as shown. Output is zero volts with no light and increases with increasing illumination. If your light source is focused to a small area, be sure that it is properly aimed to fall on the photodiode. If a narrowly focused light source were to miss the photodiode area and fall only on the op amp circuitry, the OPT301 would not perform properly. The large (0.090 x 0.090 inch) photodiode area allows easy positioning of narrowly focused light sources. The photodiode area is easily visible—it appears very dark compared to the surrounding active circuitry. The incident angle of the light source also affects the apparent sensitivity in uniform irradiance. For small incident angles, the loss in sensitivity is simply due to the smaller effective light gathering area of the photodiode (proportional to the cosine of the angle). At a greater incident angle, light is reflected and scattered by the side of the package. These effects are shown in the typical performance curve “Response vs Incident Angle.” DARK ERRORS The dark errors in the specification table include all sources. The dominant error source is the input offset voltage of the op amp. Photodiode dark current and input bias current of the op amp are approximately 2pA and contribute virtually no offset error at room temperature. Dark current and input bias current double for each 10 °C above 25°C. At 70°C, the error current can be approximately 100pA. This would produce a 1mV offset with R F = 10MΩ. The OPT301 is useful with feedback resistors of 100M Ω or greater at room temperature. The dark output voltage can be trimmed to zero with the optional circuit shown in Figure 3. FIGURE 1. Basic Circuit Connections. Photodiode current, I D, is proportional to the radiant power or flux (in watts) falling on the photodiode. At a wavelength of 650nm (visible red) the photodiode Responsivity, R I, is approximately 0.45A/W. Responsivity at other wavelengths is shown in the typical performance curve “Responsivity vs Wavelength.” The typical performance curve “Output Voltage vs Radiant Power” shows the response throughout a wide range of radiant power. The response curve “Output Voltage vs Irradiance” is based on the photodiode area of 5.23 x 10–6m2. The OPT301’s voltage output is the product of the photodiode current times the feedback resistor, (I DRF). The internal feedback resistor is laser trimmed to 1M Ω ±2%. Using this resistor, the output voltage responsivity, R V, is approximately 0.45V/ µW at 650nm wavelength. An external resistor can be used to set a different voltage responsivity. For values of R F less than 1MΩ, an external capacitor, C EXT, should be connected in parallel with RF (see Figure 2). This capacitor eliminates gain peaking and prevents instability. The value of C EXT can be read from the table in Figure 2. LIGHT SOURCE POSITIONING The OPT301 is 100% tested with a light source that uniformly illuminates the full area of the integrated circuit, including the op amp. Although all IC amplifiers are light-sensitive to some degree, the OPT301 op amp circuitry is designed to minimize this effect. Sensitive junctions are shielded with metal, and differential stages are cross-coupled. Furthermore, the photodiode area is very large relative to the op amp input circuitry making these effects negligible. FIGURE 2. Using External Feedback Resistor. EXTERNAL R F C EXT 100M Ω (1) 10M Ω (1) 1M Ω (1) 330k Ω 30pF 100k Ω 130pF 33k Ω 180pF 10k Ω 350pF NOTE: (1) No C EXT required. I D is proportional to light intensity (radiant power). 1M Ω OPT301 40pF 75 Ω 2 83 5 4 1 V O –15V +15V 0.1µF 0.1µF V O = ID RF R F I D I D (0V) λ NOTE: Metal package is internally connected to common (Pin 8). 1M Ω OPT301 40pF 75 Ω 83 5 4 1 V O = ID RF V– λ V+ R F C EXT 2 |
Số phần tương tự - OPT301M |
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Mô tả tương tự - OPT301M |
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