hello there
I want to learn about the relationship about the figure 6-9 low -side frequency response vs ALC and 7.4.1 Idc loop has a high pass cutoff frequency of 100hz.
how to understand this two part.
BRs,
Shubiao
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hello there
I want to learn about the relationship about the figure 6-9 low -side frequency response vs ALC and 7.4.1 Idc loop has a high pass cutoff frequency of 100hz.
how to understand this two part.
BRs,
Shubiao
add one more question
ALC loop, why the idc loop has a high pass cut off frequency.
my understanding is it needs a low pass cut off frequency to cancel the ambient light effect, as the ambient light produce DC current pass though the APD.
BRs,
Shubiao
Hello Shubiao,
That is correct. The ambient light cancellation circuit internal to the device can be used instead of AC coupling between the photodiode and the amplifier or via bootstrapping. If enabled, the frequency response shows a high pass filter which it's frequency cutoff will depend on the internal gain setting (2kOhm or 20kOhm). Any frequency below the cutoff will be heavily mitigated or not be present at the output.
This short blog covers AC coupling and high pass filtering. Image below is from this site.
An important note: DC/Ambient light cancellation only works when the photodiode sinking current as explained in sections 7.1 and 7.3.2 in the datasheet.
Thank you,
Sima