Amplifier for use in time-sharing applications
First Claim
1. A differential amplifier having an inverting input terminal and a noninverting input terminal and at least one output terminal, comprising four transistors forming an input stage of the differential amplifier and coupled to the inverting and noninverting input terminals and to the output terminal, such that at least two of the transistors are capable of being switched between the inverting and noninverting input terminals on different phases of a clock signal capable of driving the differential amplifier.
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Accused Products
Abstract
A differential amplifier has (at least) four input-stage transistors that are switchably coupled to the inverting and noninverting input terminals and to the output terminal(s). In one embodiment, two of the transistors are permanently coupled between the input and output terminals, while the other two transistors are switchably coupled the input and output terminals, such that, during two-phased operations, each of the switchably coupled transistors is alternately connected in parallel to a different one of the two permanently coupled transistors. In this way, any charge (due to input capacitance) in one input-stage transistor from the previous clock phase will tend to negate similar charge in another input-stage transistor at the start of each clock phase. Such an amplifier can be efficiently used in time-sharing applications. For example, when used as the amplifier shared between two stages of a pipelined analog-to-digital converter, crosstalk between stages otherwise due to input capacitance of the amplifier can be reduced and possibly eliminated.
13 Citations
14 Claims
- 1. A differential amplifier having an inverting input terminal and a noninverting input terminal and at least one output terminal, comprising four transistors forming an input stage of the differential amplifier and coupled to the inverting and noninverting input terminals and to the output terminal, such that at least two of the transistors are capable of being switched between the inverting and noninverting input terminals on different phases of a clock signal capable of driving the differential amplifier.
- 8. An integrated circuit having a differential amplifier comprising an inverting input terminal and a noninverting input terminal and at least one output terminal, the differential amplifier comprising four transistors forming an input stage of the differential amplifier and coupled to the inverting and noninverting input terminals and to the output terminal, such that at least two of the transistors are capable of being switched between the inverting and noninverting input terminals on different phases of a clock signal capable of driving the differential amplifier.
Specification