Embodiments of an apparatus that includes a substrate and an inductor residing in the substrate are disclosed. In one embodiment, the inductor is formed as a conductive path that extends from a first terminal to a second terminal. The conductive path has a shape corresponding to a two-dimensional (2D) lobe laid over a three-dimensional (3D) volume. Since the shape of the conductive path corresponds to the 2D lobe laid over a 3D volume, the magnetic field generated by the inductor has magnetic field lines that are predominately destructive outside the inductor and magnetic field lines that are predominately constructive inside the inductor. In this manner, the inductor can maintain a high quality (Q) factor while being placed close to other components.

An input buffer circuit includes an input differential amplifier unit, a differential amplifier stage, and a buffer. The input differential amplifier unit has input terminals and at least one output terminal, wherein at least two of the input terminals of the input differential amplifier unit are configured to be capacitively coupled respectively so as to provide at least one pair of signal paths for a first input signal and a second input signal of a differential input signal. The differential amplifier stage, coupled to the input differential amplifier unit, has first and second differential input terminals, and a corresponding output terminal, wherein the first and second differential input terminals are capable of being coupled to the first input signal and the second input signal respectively. The buffer, coupled to the output terminal of the differential amplifier stage, is used for outputting an output single-ended signal.

A power amplifier circuit includes: a high pass filter that has one end into which a high frequency input signal is inputted; a first amplifier that amplifies the high frequency input signal outputted from the other end of the high pass filter and outputs a high frequency signal obtained through the first amplification; a second amplifier that amplifies the high frequency signal and outputs a high frequency output signal obtained through the second amplification; an automatic transformer that performs impedance matching between the first amplifier and the second amplifier; and an impedance circuit, one end of which is electrically connected with the other end of the high pass filter, the other end of which is electrically connected with an output terminal of a bias circuit outputting bias voltage or bias current to the first amplifier, and that outputs the high frequency input signal to the bias circuit.

A class-D amplifier with multiple “nested” levels of feedback. The class-D amplifier surrounds an inner feedback loop, which takes the output of a switching amplifier and corrects for errors generated across the switching amplifier, with additional feedback loops that also take the output of the switching amplifier.

An ultra-low power sub-threshold g.sub.m stage is disclosed where transconductance is very stable with process, temperature, and voltage variations. This technique can be implemented in a differential amplifier with constant gain and a second order biquad filter with constant cut off frequency. The amplifier gain can achieve a small temperature coefficient of 48.6 ppm/° C. and exhibits small sigma of 75 mdB with process. The second order biquad can achieve temperature stability of 69 ppm/° C. and a voltage coefficient of only 49 ppm/mV.

A radio frequency module includes a module board including a first principal surface and a second principal surface on opposite sides thereof, a transmission power amplifier, a control circuit that controls the transmission power amplifier, and a first inductor connected to an output terminal of the transmission power amplifier. The control circuit is disposed on the first principal surface, and the first inductor is disposed on the second principal surface.

A radio frequency circuit is capable of sending a transmit signal of a first communication band and a transmit signal of a second communication band simultaneously and includes a transmit input terminal, a power amplifier capable of amplifying a transmit signal of the first communication band, and a filter connected between the transmit input terminal and an input terminal of the power amplifier. In the filter, a pass band is a band including a transmit band of the first communication band, and an attenuation band is a band including a transmit band of the second communication band.

A device includes an amplifier having inverting and non-inverting inputs and an output. The device includes a capacitor coupled to a first node and to ground, a resistor coupled to the first node and the amplifier output, and a first switch coupled to the first node and a current sink, which is coupled to ground. The device includes AND gate having inputs and an output coupled to control terminal of first switch. The device includes a first comparator having non-inverting and inverting inputs and an output coupled to an AND gate input; a second comparator having a non-inverting input coupled to the amplifier output, an inverting input coupled to a transistor stack, and an output coupled to an AND gate input; and a second switch coupled to the transistor stack and to a current source, the second switch having a control terminal coupled to the first comparator output.

A receiver includes an amplifier that receives a transmission signal and amplifies a first voltage difference between the transmission signal and a reference signal to generate a first output signal and a second output signal at a first node and a second node. An equalizer is provided, which is connected to the first node and the second node and receives the transmission signal. The equalizer compensates a common-mode offset between the first output signal and the second output signal based on a second voltage difference between an average voltage level of the transmission signal and the reference signal.

An offset-cancellation circuit having a first amplification stage with a gain of the first amplification stage and configured to receive an offset voltage of a first amplifier. A storage element is configured to be coupled to and decoupled from the first amplification stage and configured to store a potential difference output by the first amplification stage. The potential difference is determined by the offset voltage of the first amplifier and the gain of the first amplification stage. A second amplification stage is coupled to the storage element and configured to receive the potential difference from the storage element when the storage element is decoupled from the first amplification stage and configured to deliver an offset-cancellation current. The offset-cancellation current is determined by the potential difference and a gain of the second amplification stage.