An apparatus and method for analog to digital conversion of analog input signals are disclosed herein. In some embodiments, an analog-to-digital (ADC) may comprise: a first successive approximation register (SAR) circuit comprising a fast SAR (FSAR) circuit and a residue digital-to-analog converter (RDAC) circuit and a residue amplifier circuit, coupled to the RDAC circuit, comprising an amplifier circuit that is configured to amplify a residual signal generated by the RDAC circuit, wherein the amplifier circuit comprises a deadzone control circuit and a first, second and third inverter stages, wherein the third stage is biased to operate in a sub-threshold region.

This disclosure is directed to reducing output voltage distortions of Variable Gain Amplifiers (VGAs). A VGA may include a number of amplifiers each providing a portion of a total gain of the VGA. For example, a processing circuit may select one or more of the amplifiers of the VGA to provide the output signal with a selected gain. However, the selected amplifiers may provide amplified signals with one or more distortion signals when receiving a bias voltage. Systems and methods are described to reduce or cancel the distortion signals of the selected amplifiers by providing a subthreshold nonzero bias voltage (e.g., a weak voltage) to the remaining (e.g., non-selected) amplifiers of the VGA. For example, the non-selected amplifiers may receive the weak voltage to provide distortion signals with similar voltage amplitude and out of phase compared to the distortion signals of the selected amplifiers.

The invention relates to a mixer circuit, which includes a transconductance stage circuit, a switch stage circuit and a load stage circuit which are electrically connected in sequence. The transconductance stage circuit is used to access a radio frequency voltage signal and convert the radio frequency voltage signal into a radio frequency current signal The switch-level circuit is used to access the local oscillator signal and the radio frequency current signal, and the switch-level transistor is turned on by using the local oscillator signal; the load-level circuit is used to convert the intermediate frequency current signal into a voltage signal for output. In the present invention, the transconductance stage circuit adopts a transistor superposition technology structure, which improves the conversion gain of the mixer; at the same time, it uses a source degenerate inductance structure, which further improves the conversion gain and linearity of the circuit.

The present invention relates to a multi-stage and feed forward compensated complimentary current field effect transistor amplifiers, enabling a charge-based approach that takes advantage of the exponential properties incurred in sub-threshold operation. A plurality of complimentary pairs of novel current field effect transistors are connected in series to form a multi-stage amplifier.

The invention relates to a mixer circuit, which includes a transconductance stage circuit, a switch stage circuit and a load stage circuit which are electrically connected in sequence. The transconductance stage circuit is used to access a radio frequency voltage signal and convert the radio frequency voltage signal into a radio frequency current signal The switch-level circuit is used to access the local oscillator signal and the radio frequency current signal, and the switch-level transistor is turned on by using the local oscillator signal; the load-level circuit is used to convert the intermediate frequency current signal into a voltage signal for output. In the present invention, the transconductance stage circuit adopts a transistor superposition technology structure, which improves the conversion gain of the mixer; at the same time, it uses a source degenerate inductance structure, which further improves the conversion gain and linearity of the circuit.

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.

The present invention relates to an improvement to a current field effect transistor and trans-impedance MOS devices based on a novel and inventive compound device structure, enabling a charge-based approach that takes advantage of sub-threshold operation, for designing analog CMOS circuits. The present invention further relates to a super-saturation current field effect transistor (xiFET), having a source, a drain, a diffusion, a first gate, and a second gate terminals, in which a source channel is defined between the source and diffusion terminals, a drain channel is defined between the drain and diffusion terminals. The first gate terminal is capacitively coupled to the source channel; and the second gate terminal is capacitively coupled to said drain channel. The diffusion terminal receives a current causing change in diffused charge density throughout said source and drain channel. The xiFET provides a fundamental building block for designing various analog circuits.

The present invention relates to a novel and inventive compound device structure for a low noise current amplifier or trans-impedance amplifier. The trans-impedance amplifier includes an amplifier portion, which converts current input into voltage using a complimentary pair of novel n-type and p-type current-injection field-effect transistors (NiFET and PiFET), and a bias generation portion using another complimentary pair of NiFET and PiFET. Trans-impedance of NiFET and PiFET and its gain may be configured and programmed by a ratio of width (W) over length (L) of source channel over the width (W) over length (L) of drain channel (W/L of source channel/W/L of drain channel).

The present invention relates to a multi-stage and feed forward compensated complimentary current field effect transistor amplifiers, enabling a charge-based approach that takes advantage of the exponential properties incurred in sub-threshold operation. A plurality of complimentary pairs of novel current field effect transistors are connected in series to form a multi-stage amplifier.

The present invention relates to a novel and inventive compound device structure for a low noise current amplifier or trans-impedance amplifier. The trans-impedance amplifier includes an amplifier portion, which converts current input into voltage using a complimentary pair of novel n-type and p-type current field-effect transistors (NiFET and PiFET) and a bias generation portion using another complimentary pair of NiFET and PiFET. Trans-impedance of NiFET and PiFET and its gain may be configured and programmed by a ratio of width (W) over length (L) of source channel over the width (W) over length (L) of drain channel (W/L of source channel/W/L of drain channel).