BioSemi.nl

[poppypetal]

Hi,

I have been reading your research papers on the design of a multi-channel biosignal amplifier - thank you for posting them, they are very informative.

The papers are quite old now however, (about 10 years), so do you think that the design concepts are still applicable, or have they been surpassed by more recent technology.

Thanks

John

[Coen]

The considerations concerning the measurement situation and general setup of the acquisition system are still very valid. However, because of the new opportunities offered by modern electronic components. the hardware implementation examples in the papers can not be regarded as state-of-the-art anymore.

You will see that the general system setup of our current ActiveTwo system is very much based on the theory in the papers. For example: optimal isolation of the front-end (miniaturization, battery power supply, fiber-optic data transfer) and prevention of interference pickup by electrode cables (active electrodes) have been the main design principles.

The hardware implementation in the papers is generally obsolete. For example, at the time (10-15 years ago), it was still possible to improve on commercially available integrated operational amplifiers by using a custom designed input stage with discrete transistors. With the current availability of low-noise micropower CMOS ICs, designing your own input stage is not really worthwhile anymore. Another example is the need of an AC coupled amplifier. The recent introduction of low-power 24-bit analog-to-digital converters has made it possible to eliminate all highpass filtering from the hardware, and to use a true DC amplifier design. Consequently, our recent ActiveTwo system does not use the designs anymore as described in the published papers. The ActiveTwo design is based on careful selected opamp ICs, a DC amplifier configuration, and 24-bit analog-to-digital conversion. In general, modern electronic components has allowed to do many things in software now, that had to be done in hardware in the old days. The advantage for the customer is that the systems have become more flexible, reliable, and easier to operate. In addition, higher integration can be achieved (256 channels in approx the same box as a 32-channel amp of ten years ago), and production cost could be reduced leading to cheaper systems.

Best regards, Coen (BioSemi)

[poppypetal]

Hi Coen,

Thanks very much for your full response. I thought that this may be the case. Your papers are very useful for providing some outlines of the measurement requirements. My knowledge in the area of electronics is sketchy, but at least the human physiology signals are still relatively stable!

Once again, thanks for your post.

Regards

John

[walrus]

[quote="poppypetal"]Hi Coen,

Your papers are very useful for providing some outlines of the measurement requirements. [/quote]

May I ask where is the paper posted?

I also hope to have a quick look.

[Coen]

http://www.biosemi.com/publications.htm , bottom of the page.