Method and apparatus for nonlinear compensation
AssigneeAT&T Corp.
InventorDavid B. Doak
Life of this patent
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Abstract
A method and apparatus for compensating for nonlinear responses of capacitive loads using a load reference element.
Claims17
A pre-amplifier arrangement for providing compensation for linearizing the nonlinear current response of capacitive loads comprising,
- a load reference element having substantially the same nonlinear characteristics as said load and a capacitance vs. voltage response characteristic substantially identical to that of said load,
- said load reference element being connected between said amplifier input and output connections so that the same voltage across said capacitive load is across said reference element;
- and
- a first network connected to the input of said amplifier having a frequency zero (fz) complementing the frequency pole (fp) of said load reference element so as to cancel one another thereby providing linear current flow in nonlinear capacitive loads.
A method for providing compensation for an amplifier circuit driving capacitive loads to minimize undesired harmonic distortion in the current waveform through such capacitive loads comprising
- selecting a reference element having capacitance vs. voltage response characteristics substantially identical to those of the load whose waveform response contains the undesired harmonic distortion,
- utilizing the reference element in said amplifier circuit to alter the driving voltage waveform so as to non-linearize the amplified voltage waveform predictably in anticipation of the undesired harmonic distortion created by the load, and
- coupling the non-linearized amplified voltage waveform to said load wherein the capacitance vs. voltage characteristic of the load transforms the non-linearized voltage waveform to a linearized current waveform without harmonic distortion.
A compensation circuit for nonlinear response capacitive loads which eliminates the need for feedback loops interconnected with said load comprising;
- a first network having a load reference element with substantially the same non-linear response characteristics as said load and a capacitance vs. voltage response characteristic substantially identical to that of said load,
- a second network having a frequency zero (fz) opposite a frequency pole (fp) of said first network which complements one another, and
- an amplifier with input signal coupled through second network and said first network being connected to said amplifier input and to said load so that the same voltage is across both the first network and said load thereby forming a local feedback circuit from amplifier output to said input.
A high voltage amplifier circuit arrangement for driving a piezoelectric actuator which comprises a plurality of ceramic wafers and exhibits the nonlinear response characteristics of a large capacitive load including:
- a first network comprising a resistor/capaciter combination having a zero frequency response characteristic defined by 1/2.pi.RC Hz,
- said first network connected to an input of said amplifier circuit,
- a local feedback network comprising a ceramic wafer in combination with a resistor connected between an output of said amplifier circuit and said input, and
- the pole frequency response of said local feedback network being equal to 1/2.pi.RC Hz where the value of C is the capacitive value of said wafer.
A circuit arrangement for providing a high-voltage drive to a load including a plurality of ceramic wafers while also compensating for the nonlinear response characteristic of the capacitive nature of such loads comprising
- an operational amplifier having an input and output,
- a first input network comprising a first capacitor and a first resistor connected in parallel through which input signals are provided to said amplifier,
- a local feedback circuit comprising at least one ceramic wafer of the same type as those comprising said load connected in parallel with a second resistor,
- said local feedback circuit being connected between said input and output of said operational amplifier, and wherein the frequency response of said first input network is opposite and cancels the frequency response of said local feedback circuit.
Dependencies are inferred from the claim text.