Selectable mode transmitter driver

A transmitter comprising:

• a serializer;
• and
• a transmitter driver having one or more driver slices in parallel, each driver slice comprising:
• a transmitter driver circuit comprising:
• a main voltage-mode driver circuit connected to an input port and an output port, the main voltage-mode driver circuit configured to receive an input signal at the input port and to drive an output signal at the output port based on the input signal;
• a secondary circuit connected to the input port and the output port in parallel with the main voltage-mode driver circuit, the secondary circuit comprising:
• a secondary voltage-mode driver circuit;
• a current source connected to the secondary voltage-mode driver circuit and controllable to enable or disable a current boost to the output signal;
• and
• a switch connected to the secondary voltage-mode driver circuit and controllable to enable or disable the secondary voltage-mode driver circuit to drive the output signal in parallel with the main voltage-driver circuit.

A method of driving an output signal at a transmitter, wherein the transmitter comprises a transmitter driver circuit comprising:

• a main voltage-mode driver circuit connected to an input port and an output port, the main voltage-mode driver circuit configured to receive an input signal at the input port and to drive an output signal at the output port based on the input signal;
• a secondary circuit connected to the input port and the output port in parallel with the main voltage-mode driver circuit, the secondary circuit comprising:
• a secondary voltage-mode driver circuit;
• a current source connected to the secondary voltage-mode driver circuit and controllable to enable or disable a current boost to the output signal;
• and
• a switch connected to the secondary voltage-mode driver circuit and controllable to enable or disable the secondary voltage-mode driver circuit to drive the output signal in parallel with the main voltage-driver circuit;
• the method comprising controlling the transmitter driver circuit to operate in one of:
• a first mode of operation in which the current source is turned off and the switch is turned off, wherein the output signal is driven only by the main voltage-mode driver circuit;
• a second mode of operation in which the current source is turned on and the switch is turned off, wherein the output signal is driven by the main voltage-mode driver circuit with the current boost provided by the current source;
• and
• a third mode of operation in which the current source is turned off and the switch is turned on, wherein the output signal is driven by the main voltage-mode driver circuit and the secondary voltage-mode driver circuit in parallel.