Differential amplifier with large input common mode signal range
First Claim
1. A differential amplifier, comprising:
- a differential input capable of receiving a differential signal;
a first differential pair coupled to said differential input;
a second differential pair, coupled to said differential input, and connected in parallel with said first differential pair at a differential output; and
a differential offset circuit, coupled between said differential input and said second differential pair, and capable of level shifting said differential signal from a first level to a second level, said differential offset circuit having a first source follower coupled between a first input terminal of said differential input and a first amplifying transistor of said second differential pair and a second source follower coupled between a second input terminal of said differential input and a second amplifying transistor of said second differential pair.
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Abstract
A design for a differential amplifier with a large input common mode signal range. The differential amplifier comprises two differential pairs, each having two amplifying MOSFETs. A source follower is connected to the gate terminal of each amplifying MOSFET in one of the differential pairs. A differential signal applied to the differential amplifier comprises two separate signal. Each separate signal is applied to the gate terminals of both the amplifying MOSFET in the differential pair not driven by the source follower and the driven MOSFET of the source follower. The differential amplifier further comprises a pair of switch MOSFETs connected to a current source MOSFET. The switch MOSFETs act to control the distribution of the total current flowing from the current source MOSFET and, consequently, to determine which differential pair works dominantly to amplify the input signals. Each source follower acts to offset the voltage of its input signal to compensate for the range loss due to the bias voltages and the threshold voltages within the differential amplifier.
19 Citations
20 Claims
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1. A differential amplifier, comprising:
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a differential input capable of receiving a differential signal;
a first differential pair coupled to said differential input;
a second differential pair, coupled to said differential input, and connected in parallel with said first differential pair at a differential output; and
a differential offset circuit, coupled between said differential input and said second differential pair, and capable of level shifting said differential signal from a first level to a second level, said differential offset circuit having a first source follower coupled between a first input terminal of said differential input and a first amplifying transistor of said second differential pair and a second source follower coupled between a second input terminal of said differential input and a second amplifying transistor of said second differential pair. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An amplifier, comprising:
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an input capable of receiving an input signal;
a first amplifying transistor coupled to said input;
a second amplifying transistor, coupled to said input, and connected in parallel with said first amplifying transistor at an output; and
an offset circuit, coupled between said input and said second amplifying transistor, and capable of level shifting said input signal from a first level to a second level, said offset circuit having a source follower coupled between said input and said second amplifying transistor. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of extending an input signal range of a component that receives the input signal, comprising the steps of:
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(1) level shifting a voltage of the input signal;
(2) selecting a subcomponent, from a plurality of subcomponents within the component, to amplify said level shifted voltage; and
(3) amplifying said level shifted voltage within the component. - View Dependent Claims (20)
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Specification