Input driver for a differential folder employing a static reference ladder
AssigneeInternational Business Machines Corporation
InventorJoe Martin Poss
Life of this patent
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Abstract
An input driver for use with a differential folder in a flash A/D converter having a static ladder that provides an array of reference voltages and a method of operation thereof. The input driver includes a differential signal driver, coupled to an AC input signal, that generates first and second complementary drive signals for a differential folder stage. A tracking circuit, coupled to the differential signal driver, is utilized to maintain a voltage at the center of the static ladder to improve common mode rejection of the input driver without reducing bandwidth. In a related embodiment, the voltage at the center of the static ladder is an average DC voltage of the first and second drive signals.
Claims18
A circuit having an input driver and a static ladder that provides an array of reference voltages for use in a differential folder, wherein the input driver comprising:
- a differential signal driver, coupled to an AC input signal, that generates first and second complementary drive signals;
- and
- a tracking circuit, coupled to said differential signal driver and said static ladder, that maintains a voltage at a center of said static ladder to improve common mode rejection of said input driver without reducing bandwidth.
A method for improving common mode rejection without reducing bandwidth of a differential folder having a static ladder, comprising the steps of:
- generating first and second complementary drive signals utilizing a differential signal driver, wherein said differential signal driver is coupled to an AC input signal;
- and
- maintaining a voltage at a center of said static ladder that provides an array of reference, voltages utilizing a tracking circuit, wherein said voltage is an average DC voltage of said first and second complementary drive signals.
A differential folder, comprising:
- at least one folding stage, said folding stage including a differential pair of first and second sets of differential amplifier pairs;
- a static ladder, coupled to a supply voltage, that generates an array of reference signals to said first and second sets of differential amplifier pairs;
- and
- an input driver, coupled to an AC input signal, including:
- a differential signal driver that generates first and second drive signals for said first and second sets of differential amplifier pairs, respectively;
- and
- a tracking circuit, coupled to said differential signal driver and said static ladder, that maintains a voltage at a center of said static ladder to improve common mode rejection of said input driver without reducing bandwidth.
Dependencies are inferred from the claim text.