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AHi,
Thank you for reading.
I am designing small current sensing. And I read https://training.ti.com/high-speed-transimpedence-amplifier-design-flow
But some of them are talking about photodiodes, and my application may be different.
My requirements include:
Low input resistance, let say <50ohms
Large current dynamic range: 1uA to 1mA (Post-VGA/PGA may be needed)
High bandwidth > 10MHz is preferred.
After this analog front-end, I would prefer a 10-bit ADC with 0-1.8V input range.
And my input devices can be seen as a resistor, not like photodiodes with a capacitor. My parallel capacitor is small.
My confusion includes:
Why do we need capacitor feedback? Is it used for Gain compensation?
If my measuring devices are just a resistor, can we remove the capacitor feedback?
And one of the workable solutions I can use is OPA380. Maybe TI doesn't provide suitably PGA, so I think the post-PGA can be AD8253 by ADI (https://www.analog.com/media/cn/technical-documentation/data-sheets/AD8253_cn.pdf). Sorry to talk your competitive company here. But I would be happy to see if TI provides similar products.
I don't want VGA because it is hard to control the gain exactly accurate and I need another DAC.
But maybe VCA820 is a good backup.
So my final design may be :
1ua to 1mA -> Transimpedance AMP -> PGA (1 to 1000) -> 10-bit 100MSPS ADC
I would be grateful if you can give me some suggestions.
Thank you very much!
