Hello everyone,

I'm working on a EMG circuit and I have already ordered my components.

I've ordered INA826AIDR for the pre-amp part of my design. It seems a good instrumentation amplifier

http://www.ti.com/product/ina826

But when I compare it with INA128 which is also highly recommended for medical signal acquisition, I noticed that INA826 has a very high input bias current like 65nA whereas INA128 has only 5nA.

Do you think I should order a new instrumentation amplifier before it's too late or it doesn't matter that much and I worry myself needlessly ?

By the way, INA128 costs nearly as much as the rest of the design with delivery costs.

Or do you have another point to tell me that I should pay attention?

 

If you cannot tell ahead of time, try the INA826AIDR and see if it meets your specifications.

 

Try some Tsingtaeo Chinese beer. Buy a case of it. Money better spent.

 

The input bias current causes input voltage offset due to this current flowing through impedance seen by the inputs. So whether it's a problem depends upon your input impedances and the input signal levels.

 

Thank you guys for the answer,

As I don't know the magnitude of the signal I'm trying to acquire yet, I'm not sure 65nA would be a problem or not. I expect something around 100uV and guess I would not be a problem.

@AlphaDesign888
Great tip

 

What is the signal source impedance?

 

As I use surface electrodes on human skin, say it is 50k ohm.
From a medical instrumentation book, these are basic requirements for pre-amp part.

There are several important properties to consider in a pre-amplifier:
• High common mode rejection ratio
• Very high input impedance
• Short distance to the signal source
• Strong DC signal suppression

By the way, I've just received my order: INA826AIDR. Such a fool I am, I didn't pay attention when ordering, it is SOIC size. I cannot use it on my breadbord. I just ordered INA128PA therefore.

http://www.ti.com/product/INA128/description