Analog Section Schematics

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Power System

Two 5 Volt regulators powered by 9 Volts from batteries.  Single supply operation with an additional split voltage (2.5V) generated by the A/D.

 

Protection Circuit

Two sets of matched transistors configured as diodes that limit incoming channel voltages to ~1.4V with a single pole filter to bandlimit to 1kHz.

Mode Switch and Amplification

2 pole 3 throw switch selects EEG or EMG gain stages or calibration gain stage.  The calibration gain stage sends a known signal through channel in order to find gain value from adjustable gain pot.

 

Right Leg Driver

Inverts and amplifies common mode signal originating in the body.  Output is remixed into body to cancel common mode effects.

 

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