DIGITAL-TO-ANALOG SINUSOIDAL DRIVER APPARATUS, SYSTEMS AND METHODS

摘要

Input codes are sequenced at a lower-resolution linear DAC and the output is converted to a linear current waveform. A first of two interconnected analog current multipliers multiplies the linear current by itself and by the inverse of a first constant current source to create a quadratic current output. A second current multiplier multiplies the quadratic output current by the linear current and by the inverse of a second constant current source to generate a cubic current output. The quadratic and cubic currents are subtracted from the linear current to generate an approximation of the first 180 degrees of a sine wave current. Alternate (pi to 2*pi) positive-going one-half sine waves may be polarity reversed to create a complete positive-going and negative-going sine-shaped electrical current of higher resolution than is available from a sine DAC of resolution equivalent to that of the lower-resolution linear DAC.

主权项

1. A method of digitally creating a one-half sinusoidal electrical drive current, comprising:
at an input to a linear digital-to-analog converter (DAC) and at regular intervals, presenting a set of input codes in increasing numerical sequence starting with a code to generate a smallest output voltage magnitude V(0) and ending with a code to generate a largest output voltage magnitude (“V(Max_DAC_Code”)); at the input to the linear DAC and at regular intervals, presenting the set of input codes in decreasing numerical sequence starting with the code to generate V(Max_DAC_Code) and ending with a code to generate V(0), a magnitude of each DAC output voltage referred to as V(DAC_Code) (“V(c)”); at a transconductance amplifier, converting each V(c) to a corresponding linear electrical current I(c); at a first analog multiplier, multiplying a magnitude of each I(c) by itself and by an inverse of a magnitude of a first constant current source IA to generate a first multiplier output current {[I(c)]2/IA}; at the second analog multiplier, multiplying each first multiplier output {[I(c)]2/IA} by the linear current I(c) and by an inverse of a second constant current source IB to generate a second multiplier output current {[I(c)]3/(IA*IB)}; at a summing junction, subtracting each first multiplier output current {[I(c)]2/IA} and each second multiplier output current {[I(c)]3/(IA*IB)} from the corresponding linear electrical current I(c) to generate a set of output currents I_OUT(c) as the one-half sinusoidal electrical drive current.