On 4/14/22 9:54 AM, ed breya wrote:
The low noise opamps are indeed designed for the feature, and they tell you about it, and how and why. The trade-offs are usually input bias current being quite high (due to bigger or paralleled transistors running at fairly high currents), and only good for a low resistance environment.
Actually not exactly - Parts like the OPA656 have about 6 nV/sqrt(Hz) voltage noise and tiny fA/sqrt(Hz) current noise, and are intended for use in high Z circuits.
The ADA4817 is about 4 nV/sqrt(Hz) and the OPA2810 (dual) and OPA810 (single) are buffers with 6nV/Sqrt(Hz) and 5 fA/sqrt(hz). The AD8001 is a current feedback amp (normally for low Z) and is 2nV/sqrt(Hz), but 2 pA/sqrt(Hz) on the non-inverting input, so a 1M input source will turn that into 2mV, which is pretty large. There's some folks who have combined a FET source follower with the AD8001.
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