I have tried to design an surface Electromyograph front end sensor, using the TI INA118P instrumentation amplifier IC with a stage 1 gain of 20...followed by two filters ( a high pass filter of 10Hz cut off and a low pass filter of 300 Hz) to band-limit the signal between 10-300Hz...(active 1st order filters using IC TLC 272). Also, i'd put in an elbow drive circuit. But I have noticed that a bias voltage of around 1V,200mHz had to be applied, to get the output..else the circuit wouldn't work....is there any way i can eliminate the need for this bias input...??
Hello Varun. The In amp IN118P has a relatively high input bias current (over 1 nA). This may be cause of a built of voltage in a capacitor in your circuit.
If I see your schematics, may be able to answer your question more precisely.
In most of physiological amplifications there is a feedback system to prevent building up of charge build up. Best regards A.Izad
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