Other Parts Discussed in Thread: LMH34400
Hi there,
Now we are planning to build a photodetector circuit, the signal frequency is 100MHz, and the expected photocurrent is around 1uA (the junction capacitance of the PD is about 1.5pF). But the trouble is that the signal is actually superimposed on a DC background of about 1mA. Therefore the input to the TIA must be AC coupled.
I noticed that the LMH32401 has an ALC mode, but the manual states that there is an increase in noise with ALC mode turned on. Meanwhile, I have found some solutions using external AC coupling components, such as those listed at the following URL.
I slightly modified the first circuit, lowering resistor R1 to reduce bias variation on the PD as shown. I also noticed that the manual of LMH32401 mentions that using external AC-coupled components will also degrade the amplifier's performance. So my question is,
(1)if I'm only looking for a lower noise (board space and cost are not a concern), should I enable the ALC mode of the LMH32401, or use an external AC coupling?
(2)LMH34400 is in the preview state, and seems that it is more suitable for my application than LMH32401. So when will it be available?
