Low noise buffer circuit for increasing digital signal transition slew rates

An apparatus including a low noise buffer circuit for increasing the slew rates of transitions between signal states of a digital signal while drawing minimal transient power supply current during said signal state transitions, comprising:

• digital signal inversion means for conducting a plurality of power supply source and sink currents and in accordance therewith receiving and successively inverting an input digital signal with input rising and falling edge slew rates and in accordance therewith providing an output digital signal with output rising and falling edge slew rates which are higher than said input rising and falling edge slew rates;
• current supply means, coupled to said digital signal inversion means, for receiving a plurality of current control signals and in accordance therewith conveying said plurality of power supply source and sink currents;
• and
• control means, coupled to said digital signal inversion means and said current supply means, for receiving said output digital signal and in accordance therewith providing said plurality of current control signals;
• wherein, in accordance with said plurality of current control signals, successive alternating portions of said digital signal inversion means conduct respective ones of said plurality of power supply source and sink currents which
• include unregulated source currents and regulated sink currents during respective low-to-high output signal transitions,
• transition from said unregulated source currents and said regulated sink currents to regulated source currents and unregulated sink currents, respectively, during respective high output signal states,
• include said regulated source currents and said unregulated sink currents during respective high-to-low output signal transitions, and
• transition from said regulated source currents and said unregulated sink currents to said unregulated source currents and said regulated sink currents, respectively, during respective low output signal states.

An apparatus including a low noise buffer circuit for increasing the slew rates of transitions between signal states of a digital signal while drawing minimal transient power supply current during said signal state transitions, comprising:

• a current supply circuit configured to receive a plurality of current control signals and in accordance therewith convey a plurality of supply currents which includes a plurality of unregulated source currents, a plurality of regulated source currents, a plurality of unregulated sink currents and a plurality of regulated sink currents;
• a control circuit, coupled to said current supply circuit, configured to receive an output digital signal and in accordance therewith provide said plurality of current control signals;
• a plurality of digital signal inversion circuits, coupled to said current supply circuit and said control circuit, configured to conduct said plurality of supply currents and in accordance therewith receive and successively invert an input digital signal with input rising and falling edge slew rates and in accordance therewith provide said output digital signal with output rising and falling edge slew rates which are higher than said input rising and falling edge slew rates, wherein each one of said plurality of digital signal inversion circuits conducts a respective portion of said plurality of supply currents which
• includes an unregulated source current and a regulated sink current during a respective low-to-high output signal transition,
• transitions from said unregulated source current and said regulated sink current to a regulated source current and an unregulated sink current, respectively, during a respective high output signal state,
• includes said regulated source current and said unregulated sink current during a respective high-to-low output signal transition, and
• transitions from said regulated source current and said unregulated sink current to said unregulated source current and said regulated sink current during a respective low output signal state.