An impedance converter circuit achieves negative capacitance and/or negative inductance for radio frequency (RF) front end impedance matching for low noise amplifier (LNA) designs. The impedance converter circuit includes a first transistor coupled to a first RF input at a source of the first transistor. The impedance converter circuit also includes a second transistor coupled to a second RF input at a source of the second transistor. The second transistor is cross-coupled to the first transistor to form a cross-coupled pair of transistors. The cross-coupled pair of transistors is configured to generate a negative capacitance or a negative inductance based on a load impedance coupled to a drain of the first transistor and a drain of the second transistor.

A negative impedance circuit includes: a differential circuit stage; a positive feedback path from an output of the differential circuit stage to a first input of the differential circuit stage; and a negative feedback path from the output of the differential circuit stage to a second input of the differential circuit stage. The negative feedback path includes a first transistor, and a unitary gain path from the output of the differential circuit stage to the second input of the differential circuit stage, the unitary gain path coupled to ground via a reference impedance. The positive feedback path includes a second transistor. The first and second transistors are coupled in a current mirror arrangement and have respective control electrodes configured to be driven by the output of the differential circuit stage, where the negative impedance circuit causes a negative impedance at the first input of the differential circuit stage.

A receiving circuit and method for increasing bandwidth are provided. The receiving circuit includes a linear equalizer circuit and a variable gain amplifier. The linear equalizer circuit includes a first negative impedance converter, to generate a first capacitance. The variable gain amplifier is coupled to the linear equalizer circuit. The variable gain amplifier includes a first-stage gain circuit and a feedback circuit. The first-stage gain circuit is coupled to the feedback circuit, and the feedback circuit generates a zero-point at the output end of the first-stage gain circuit.

A chopper amplifying circuit employing a negative impedance compensation technique, including a differential input end, a first-level chopper switch, a first-level amplifying circuit, a second-level chopper switch, a second-level amplifying circuit, a negative impedance converting circuit, a negative feedback unit, an input capacitor, and a differential output end, is provided. The differential input end is connected to the first-level chopper switch. An output terminal of the first-level chopper switch is connected to the first-level amplifying circuit through the input capacitor. The first-level amplifying circuit is connected to the second-level chopper switch, which is connected to the second-level amplifying circuit. The second-level amplifying circuit is connected to the differential output end, and is also connected to a feedback input end of the first-level amplifying circuit through the negative feedback unit. The negative impedance converting circuit is parallel-connected to a signal input end of the first-level amplifying circuit.

There are disclosed various methods and apparatuses for amplifying a signal. In some embodiments of the method a signal is provided to an input (S) of a transconducting element (T) of an amplifier. An amplified signal is formed on the basis of the input signal by the transconducting element (T). The amplified signal is provided to an output stage. A negative conductance (R.sub.neg) in the output stage is used to adjust a gain and a noise figure of the amplifier. The amplified signal is provided via a feedback element (C.sub.fb) to another input (G) of the transconducting element (T). In some embodiments the apparatus comprises means for implementing the method.

An impedance converter circuit achieves negative capacitance and/or negative inductance for radio frequency (RF) front end impedance matching for low noise amplifier (LNA) designs. The impedance converter circuit includes a first transistor coupled to a first RF input at a source of the first transistor. The impedance converter circuit also includes a second transistor coupled to a second RF input at a source of the second transistor. The second transistor is cross-coupled to the first transistor to form a cross-coupled pair of transistors. The cross-coupled pair of transistors is configured to generate a negative capacitance or a negative inductance based on a load impedance coupled to a drain of the first transistor and a drain of the second transistor.

Systems, apparatuses, and methods for implementing a negative resistance circuit for bandwidth extension are disclosed. Within a feedback path of a differential signal path, capacitors are placed on the inputs and outputs of a fully differential amplifier connecting to the differential signal path. In one embodiment, a circuit includes a fully differential amplifier and four capacitors. A first capacitor is coupled between a first signal path and a non-inverting input terminal of the amplifier and a second capacitor is coupled between the first signal path and a non-inverting output terminal of the amplifier. A third capacitor is coupled between a second signal path and an inverting input terminal of the amplifier and a fourth capacitor is coupled between the second signal path and an inverting output terminal of the amplifier. The first and second signal paths carry a differential signal.

A radio frequency (RF) power amplifier circuit includes an input and an output. A power amplifier transistor has a first terminal connected to the input, a second terminal connected to the output, and a third terminal defined by a degeneration inductance. A first capacitor is connected to the third terminal of the power amplifier transistor, along with a negative capacitance circuit connected in series with the first capacitor. The negative capacitance and the first capacitor define a series resonance at a predefined operating frequency band, which shunts the degeneration inductance of the third terminal.

A radio frequency (RF) power amplifier circuit includes an input and an output. A power amplifier transistor has a first terminal connected to the input, a second terminal connected to the output, and a third terminal defined by a degeneration inductance. A first capacitor is connected to the third terminal of the power amplifier transistor, along with a negative capacitance circuit connected in series with the first capacitor. The negative capacitance and the first capacitor define a series resonance at a predefined operating frequency band, which shunts the degeneration inductance of the third terminal.

There is disclosed a matching network for connecting an electrically small antenna to an RF source or load. The matching network includes a negative impedance converter, a pre-matching network for connecting the negative impedance converter to the antenna and a post-matching network for connecting the negative impedance converter to the RF source or load. The pre-matching network comprises a combination of capacitors and/or inductors to transform both a real part and an imaginary part of an impedance of the antenna. The negative impedance converter is configured to cancel the transformed imaginary part of the impedance of the antenna. The post-matching network comprises a combination of capacitors and/or inductors to transform a residual real part of the impedance of the antenna to match an impedance of the RF source or load. There is also disclosed an antenna system comprising a plurality of antenna radiating elements each having an associated feed, at least one of the feeds being connected to an RF source or load by way of an active matching circuit comprising a pre-matching network, a negative impedance converter and a post-matching network.