One of the first challenges to be tackled concerns the power supply. The device is to run off a single 9V battery, bearing in mind that the signals will be bipolar, this would require biasing for all amplifiers and filters. We are also only interested in the envelope of the signal and so only require one half of the wave (positive or negative side). All these constraints suggest the use of a dual rail supply, removing the need to bias op amps and allowing for a bipolar wave that can then easily be rectified.
To generate a dual rail supply from a single 9V battery a virtual ground is created. This is done using the following circuit, a virtual earth driver.
As you can see from the simulation the circuit has created two voltages, referenced from the virtual ground, of +4.5V and -4.5V. Now the power supply has been sorted we can begin to retrieve the EMG signal from the muscles. The next stage is to design the input amplifier.
Dan Mannion - Electronic Engineer 
Is this emg sensor really working?? ’cause we’re going to make a project like this. Can i rely on this one??
Yes you can HOWEVER be wary of just blindly following the circuits as if it doesn’t work you won’t be able to troubleshoot. Also there may be issues with the single to dual tail circuit as we have current issues…