Amplifier with fixed input impedance operated in various gain modes
AssigneeMediatek Inc.
InventorEn-Hsiang Yeh
Life of this patent
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Abstract
An amplifier with substantially fixed input impedance being operated in a plurality of gain modes. The amplifier includes an input port for receiving an input signal, an amplifying circuit for amplifying the input signal with corresponding amplifying ratios in various gain modes, a plurality of resistive negative feedback circuits electrically connected to the input port and the amplifying circuit for keeping the input impedance substantially fixed in various gain modes, and an output port for outputting the input signal processed by the amplifying circuit.
Claims17
An amplifier with substantially fixed input impedance when operating in a plurality of gain modes, the amplifier comprising:
- an input port for receiving an input signal;
- a gain circuit for amplifying the input signal by corresponding gain ratios in various gain modes;
- a plurality of resistive negative feedback circuits selectively connected to the input port and the gain circuit for keeping the input impedance of the amplifier substantially fixed in the various gain modes, each of the various gain modes having at least one corresponding resistive negative feedback circuit that is connected only in the corresponding mode;
- and
- an output port for outputting the input signal amplified by the gain circuit.
A method used in an amplifier for keeping the input impedance of the amplifier substantially fixed in a plurality of gain modes, the method comprising:
- providing a gain circuit for amplifying an input signal by corresponding gain ratios according to the gain modes;
- providing at least one resistive negative feedback circuit for each of the various gain modes, each resistive negative feedback circuit being selectively connected to the gain circuit and the input signal;
- utilizing the gain circuit to switch the amplifier among the various gain modes that is connected only in the corresponding mode;
- and
- utilizing the plurality of resistive negative feedback circuits to keep the input impedance of the amplifier substantially fixed in various gain modes.
Dependencies are inferred from the claim text.