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Question about AD8237

Question asked by Kazu on Dec 27, 2016

Hi All,


I have five questions. Please support this case.

Data sheet page 22/29


1. Cancelling Error from FB Input Bias Current

 If the resistor which can cancel the error is not used, how much the Vout could be affected?
 I will change gain of AD8237 depends on our sensor types. I would not like to use this resistor
 if the error on the Vout is much small.

2. Clock Feedthrough

 What kind of filters do you recommend to reduce such ripple?
 Gains I will set are from 1 to 250. It depends on our sensor types.
 RC low-pass filter is enough? If other filter is recommended, please let me know it.


Data sheet page 24/29


3. Figure 72. Using Voltage Divider to Set Reference Voltage

 There is not the resistor to cancel the error from FB input bias current in this circuit.
 Additional R1//R2 resistor is needed in order to cancel the error the same as Figure 66?


Data sheet page 26/29


4. Programmable Gain with a Multiplexer
 What is the 200ohm resistor put between REF pin and GND for?
 If it is for cancelling error from FB input bias current, why 200 ohm is recommended? (200 ohm is not R1//R2)


5. Programmable Gain with a Multiplexer

 Two questions about the following explanation.
 "With the AD8237 topology, the switches can be placed in a high impedance sense path eliminating the parasitic resistance effects."
 - About the switches, they are integrated in the AD8237 or needed as external components?
 - About the parasitic resistance, what circuit or component has such resistance?


I hope that  2017 finds you happy and successful.


Thank you.