High-speed electro-optical modulator drivers and method

A modulator driver, comprising:

• a first amplifier stage (A1) having inputs and outputs, the first amplifier stage comprising a first differential pair of transistors, wherein the inputs of the first amplifier stage comprise positive and negative inputs having signal voltages and currents that are inverted with respect to each other and the outputs of the first amplifier stage comprise positive and negative outputs having signal voltages and currents that are inverted with respect to each other;
• a second amplifier stage (A2) having inputs and outputs, the second amplifier stage comprising a second differential pair of transistors, the inputs of the second amplifier stage coupled to the outputs of the first amplifier stage, wherein the inputs of the second amplifier stage comprise positive and negative inputs having signal voltages and currents that are inverted with respect to each other and the outputs of the second amplifier stage comprise positive and negative outputs having signal voltages and currents that are inverted with respect to each other;
• an active load having inputs and outputs, the inputs of the active load coupled to the outputs of the second amplifier stage;
• a feedback stage (A3) having inputs and outputs, the inputs of the feedback stage commonly coupled to the outputs of the second stage amplifier and the inputs of the active load, the outputs of the feedback stage commonly coupled to the inputs of the second stage amplifier and the outputs of the first amplifier stage, said feedback stage comprising a first feedback amplifier and a second feedback amplifier;
• and
• a first tuning network, coupled between the negative output of the second stage amplifier and the input of the first feedback stage, and a second tuning network, coupled between the positive output of the second stage and the input of the second feedback stage.

A modulator driver, comprising:

• a first amplifier stage (A1) having inputs and outputs, the first amplifier stage comprising a first differential pair of transistors, wherein the inputs of the first amplifier stage comprise positive and negative inputs having signal voltages and currents that are inverted with respect to each other and the outputs of the first amplifier stage comprise positive and negative outputs having signal voltages and currents that are inverted with respect to each other;
• a second amplifier stage (A2) having inputs and outputs, the second amplifier stage comprising a second differential pair of transistors, the inputs of the second amplifier stage coupled to the outputs of the first amplifier stage, wherein the inputs of the second amplifier stage comprise positive and negative inputs having signal voltages and currents that are inverted with respect to each other and the outputs of the second amplifier stage comprise positive and negative outputs having signal voltages and currents that are inverted with respect to each other;
• an active load having inputs and outputs, the inputs of the active load coupled to the outputs of the second amplifier stage;
• and
• a feedback stage (A3) having inputs and outputs, the inputs of the feedback stage commonly coupled to the outputs of the second stage amplifier and the inputs of the active load, the outputs of the feedback stage commonly coupled to the inputs of the second stage amplifier and the outputs of the first amplifier stage, said feedback stage comprising a first feedback amplifier and a second feedback amplifier;
• wherein the first stage amplifier has a negative output coupled to a positive input by means of a third resistor (R3), and a positive output coupled to a negative input by means of a fourth resistor (R4).

A method for operating a modulator driver, comprising:

• in a first arm of a differential modulator driver:
• amplifying a positive input voltage signal by a first amplifier to generate a first output current signal;
• amplifying the first output current signal by a second amplifier to generate a first driver output signal;
• providing a negative feedback of the first driver output signal to the positive input of the second amplifier by a first feedback amplifier;
• wherein between the amplifying and the providing steps, tuning the first driver output signal by separating the second amplifier and the first feedback amplifier by means of an inductor network;
• and
• in a second arm of a differential modulator driver:
• amplifying a negative input voltage signal by a first amplifier to generate a second output current signal;
• amplifying the second output current signal by a second amplifier to generate a second driver output signal;
• providing a negative feedback of the second driver output signal to the negative input of the second amplifier by a second feedback amplifier;
• wherein between the amplifying and the providing steps, tuning the second driver output signal by separating the second amplifier and the second feedback amplifier by means of an inductor network.