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Precision Amplifiers Forum
INA116 input protection
I am developing an amplifier for recording the electrical activity of cells. As a pre-amplifier INA116 set (differential inclusion of inputs). What kind of protection circuit inputs can be used? What kind of protection scheme is made in the INA116 inputs? Can I just put in series with each input resistor (eg 1k)?Vlad
I have a few quick questions about your application. What type of 'cells' are you referring to? Also, what is the frequency and amplitude of the transients that you expect to see on the inputs of the INA116? What is the source of the transients? Finally, please share your schematic if you can.
Precision Analog Applications
We study the snail cells. The electrical activity of the cells expressed the pulses of positive polarity in the presence of a constant negative bias (cell potential). The amplitude of the pulses to 10 mV, a constant offset to 80mV, pulse duration (3-20) ms. Since the operator manipulates the microelectrodes when connected to a cell, there is the possibility of accumulation and electrostatic charge. How to protect a preamplifier??
Can I use this feature to protect .... http://www.bourns.com/pdfs/MLU.pdf
Thanks for the additional information. I am looking into this further and will get back with you as soon as I can.
You can use the aforementioned varistor, but please note that the leakage current is 5nA. This is much greater than the input bias current of the INA116 and will therefore cause additional error.
I assume that you chose the INA116 for its extremely low input bias current to avoid current flowing in the cell. As Pete points out, these protection devices are notoriously leaky.
I suggest that you protect with 10k-ohm resistors in series with each input and 47pF capacitor at each input terminal of the INA116 to ground. This will add a high degree of immunity from ESD. If you then use reasonable precautions to minimize ESD you should have no problem.
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