Stable systems for comparing and converting signals
AssigneeAnalog Devices, Inc., a corporation organized and existing under the laws of the State of MA
InventorDavid Nairn
Life of this patent
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Abstract
Comparator systems are provided that include cross-coupled transistors which respond to a differential network that receives an input signal. The systems further include a control transistor connected across the cross-coupled transistors and a bias network configured to apply a bias voltage to the control transistor that is substantially the voltage across two transistors which are each biased into saturation. It has been found that this bias during the systems' acquire phase substantially stabilizes the systems' gain over variations in their total environment and that this stabilization enhances the systems' performance.
Claims20
A comparator system that provides a latch signal in response to an input signal, comprising:
- a differential network of transistors for receiving said input signal;
- cross-coupled transistors that respond to said differential network;
- a control transistor connected across said cross-coupled transistors and having a control terminal;
- and
- a bias network configured to apply to said control terminal:
- a) in a system latch phase, a latch bias voltage that biases off said control transistor;
- and
- b) in a system acquire phase, an acquire bias voltage that is substantially the voltage across two transistors which are each biased into conduction;
- said cross-coupled transistors thereby providing said latch signal in said latch phase.
A converter system, comprising:
- a plurality of converter stages serially connected to thereby convert an analog input signal to a corresponding digital output signal wherein at least one of said stages includes:
- a comparator system that converts a respective portion of said input signal to at least one corresponding digital bit of said output signal;
- and
- a residue generator that provides another portion of said input signal to a subsequent one of said converter stages in the form of a residue signal which said generator generates in response to said respective portion and said corresponding digital bit;
- and wherein said comparator system includes:
- a differential difference amplifier for receiving an input signal and a reference signal;
- cross-coupled transistors that respond to said differential difference amplifier;
- a control transistor connected across said cross-coupled transistors and having a control terminal;
- and
- a bias network configured to apply to said control terminal:
- a) in a system latch phase, a latch bias voltage that biases off said control transistor;
- and
- b) in a system acquire phase, an acquire bias voltage that is substantially the same as the voltage across two transistors which are each biased into conduction;
- said cross-coupled transistors thereby providing said latch signal in said latch phase.
The system of claim 18, wherein said first and second transistors are diode-coupled transistors.
Dependencies are inferred from the claim text.