Interfacing the ADL5317 High Side Current Mirror to a Translinear Logarithmic Amplifier in an Avalanche Photodiode Power Detector Application (CN0057)
This circuit uses the monitor current output, IPDM, of theADL5317 to interface directly to an Analog Devices, Inc., translinear logarithmic amplifier such as the AD8304, AD8305, ADL5306, or ADL5310. Figure 1 shows the basic connections necessary for interfacing the ADL5317 to the AD8305. In this configuration, the designer can use the full current mirror range of the ADL5317 for high accuracy power monitoring of an avalanche photodiode (APD).
Figure 1: Typical connection of ADL5317 to the AD8305 Translinear Logarithmic Amplifier
Measured rms noise voltage at the output of the AD8305 vs. input current is shown in Figure 2 for the AD8305 by itself and in cascade with the ADL5317. The relatively low noise produced by the ADL5317, combined with the additional noise filtering inherent in the frequency response characteristics of the AD8305, results in minimal degradation to the noise performance of the AD8305.
Figure 2: RMS Noise of AD8305 vs. AD8305 Cascaded with ADL5317
- High Side Current Monitor of Avalanche Photodiode
- Translinear Logarithmic Amplifier
- Wide Input Current Range 3nA - 3mA
Схемы и диаграммы
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