Design an op-amp circuit Similar to nn ECO, an electroencephalogram (I HO) is a

Question

Design an op-amp circuit

Similar to nn ECO, an electroencephalogram (I HO) is a measure of brain neural activity taken with electrodes (on the scalp). You have observed that the EEG has a maximum amplitude of 110 pV ITw signal can also have an ofl'set, which can range between *10 mV (the "offset" ta this context is etjuaJ to the mean value of the signal). You wish to get nd of the offset within its possible range and amplify the signal by 100. Design a circuit to accomplish this goal Assume that you have plusminus 15 V voltage sources, a I -turn lOkfl pot and as many op-amps as you need (Hint you need an adjustable voltage source in order to eliminate the unknown amount of offset)

Explanation / Answer

the simplaest design would need three swiches(MOS) along with one OP-AMP.

step1:

first put one switch(S3) in between output to negative terminal of the op-amp as a feedback and connect this terminal to gnd through a capacitor.

now attach the other terminal to ground through anothether switch(S2) and a resistor value 1K ohm.

put another resistor in series from the positive termina to output of value 99k.

close the switches(S2 and S3).

u can understand that here only the offset voltage will be amplified and the output voltage will be stored at the negative terminal capacitor.

measure that voltage it will be Voff*(1 + 99/1) = 100Voff where Voff is the offset voltage.

use a voltage divider to get 1/100 (using 100K ohm and 1 k ohm in series) of the output voltage and connect it to the capacitor.

step2:

now use another switch S3 and give the input voltage in positive terminal in series with the 1 K ohm resister.

S1 is complement to the S2 and S3 meaning when S2 and S3 is closed S1 is open and viceversa.

every time first close s2 and S3 having zero input voltage so it will automatically give the offset equivalent voltage to the negative input voltage.

and then when S1 is closed the offset will get cancel as alreday equivalent offset is present in the negative terminal so it will just amplify the input voltage by (1 + 99/1) = 100 times.

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