Finger biometric sensing device including series coupled error compensation and drive signal nulling circuitry and related methods

A method of reducing a relatively large drive signal in a finger biometric sensing device comprising drive circuitry capable of generating a drive signal and an array of finger biometric sensing pixel electrodes cooperating with the drive circuitry and capable of generating a detected signal based upon placement of a finger adjacent the array of finger biometric sensing pixel electrodes, the detected signal including the relatively large drive signal component and a relatively small sense signal component superimposed thereon, and at least one gain stage coupled to the array of finger sensing biometric pixel electrodes, the method comprising:

• operating drive signal nulling circuitry coupled to the at least one gain stage to reduce the relatively large drive signal component from the detected signal, the drive signal nulling circuitry comprising a first digital-to-analog converter (DAC) generating an inverted scaled replica of the drive signal for the at least one gain stage;
• and
• operating error compensation circuitry comprising a memory capable of storing error compensation data, and a second DAC coupled in series with the first DAC to compensate for at least one error in the inverted scaled replica of the drive signal based upon the stored error compensation data.

A method of reducing a relatively large drive signal in a finger biometric sensing device comprising drive circuitry capable of generating a drive signal and an array of finger biometric sensing pixel electrodes cooperating with the drive circuitry and capable of generating a detected signal based upon placement of a finger adjacent the array of finger biometric sensing pixel electrodes, the detected signal including the relatively large drive signal component and a relatively small sense signal component superimposed thereon, and at least one gain stage coupled to the array of finger sensing biometric pixel electrodes, the method comprising:

• operating drive signal nulling circuitry coupled to the at least one gain stage to reduce the relatively large drive signal component from the detected signal, the drive signal nulling circuitry comprising a first digital-to-analog converter (DAC) generating an inverted scaled replica of the drive signal for the at least one gain stage;
• and
• operating error compensation circuitry comprising a second DAC coupled in series with the first DAC to compensate for at least one error in the inverted scaled replica of the drive signal based upon the reduced relatively large drive signal component and the relatively small sense signal component.