Amplifier with common-mode filter
AssigneeQUALCOMM Incorporated
InventorsMuhammad Hassan, Bhushan Shanti Asuri, Apsara Ravish Suvarna, Youngchang Yoon
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Abstract
A differential amplifier having a tunable filter is disclosed. The tunable filter may attenuate some common-mode signals while not affecting amplification of differential signals. The tunable filter may include a resonant circuit to select frequencies of common-mode signals to attenuate. The resonant circuit may include a variable capacitor series-coupled to an inductor. A resonant frequency of the resonant circuit may be determined, in part, by a capacitance value of the variable capacitor.
Claims17
A differential amplifier, comprising:
- a differential transistor pair configured to receive differential input signals and to generate differential output signals;
- and
- a trap filter comprising an inductor configured to filter a common-mode current in the differential output signals, the trap filter further comprising a first resonant circuit configured to:
- filter the common-mode current based on a resonant frequency of the first resonant circuit;
- and
- provide a circuit path to ground when the common-mode current is substantially near the resonant frequency.
A differential amplifier, comprising:
- a differential transistor pair configured to receive differential input signals and to generate differential output signals;
- and
- a trap filter comprising an inductor configured to filter a common-mode current in the differential output signals, the trap filter comprising:
- a first capacitor having a first terminal configured to receive a first signal of the differential output signals and having a second terminal coupled to a circuit node;
- and
- a second capacitor having a first terminal configured to receive a second signal of the differential output signals and having a second terminal coupled to the circuit node.
A differential amplifier comprising:
- means for receiving differential input signals and generating differential output signals;
- and
- means for filtering a common-mode current in the differential output signals using a first resonant circuit to provide a circuit path to ground when the common-mode current is substantially near a resonant frequency of the first resonant circuit.
A method for amplifying a differential signal, comprising:
- generating, by a differential transistor pair, differential output signals based on received differential input signals;
- and
- filtering, by a trap filter comprising an inductor, a common-mode current in the differential output signals, the trap filter configured to provide a circuit path to ground when the common-mode current is substantially near the resonant frequency.
Dependencies are inferred from the claim text.