This paper presents an amplifier with low noise, high gain, low power consumption, and high linearity for electrocardiogram (ECG) recording. The core of this design is a chopper-stabilized capacitive-feedback operational transconductance amplifier (OTA). The proposed OTA has a two-stage structure, with the first stage using a combination of current reuse and cascode techniques to obtain a large gain at low power and the second stage operating in Class A state for better linearity. The amplifier additionally uses a DC servo loop (DSL) to improve the rejection of DC offsets. The amplifier is implemented in a standard 0.13 μm CMOS process, consuming 1.647 μA current from the supply voltage of 1.5 V and occupying an area of 0.97 mm². The amplifier has a 0.5 Hz to 6.1 kHz bandwidth and 59.7 dB gain while having no less than a 65 dB common-mode rejection ratio (CMRR). The amplifier’s total harmonic distortion (THD) is less than 0.1% at 800 mV_pp output. The amplifier can provide a noise level of 1.18 μV_rms in the 0.5 Hz to 500 Hz bandwidth that the ECG signal is interested in and has 3.38 μV_rms input-referred noise (IRN) over the entire bandwidth, so its noise efficiency factor (NEF) is 2.13.

A 3.3 V mode-switching RF CMOS power amplifier (PA) for WLAN applications is presented, which is integrated into a 55-nm bulk CMOS process. The proposed PA offers both static control and dynamic power control, allowing it to operate efficiently in both low-power and high-power modes. The pure low-power mode is achieved by reducing power cells, which are also used for linearization in high power mode. The low-power mode is achieved by reducing the number of power cells which are also used for linearization in the high-power mode. In the dynamic power control mode, the total AM–AM and AM–PM distortion is effectively compensated for by dynamically controlling the number of power cells and adjusting the matching input. The proposed PA achieves an output P1dB of 27.6 dBm with a PAE of 32.7% and an output P1dB of 17.7 dBm with a PAE of 10% in high-power and low-power modes, respectively. It is measured with an 802.11 n 64-quadrature-amplitude-modulation (MCS7) signal and shows a maximum average power of 19 dBm under an error-vector-magnitude (EVM) of −27 dB.

This paper presents a dual-band fully integrated high linearity CMOS power amplifier (PA). The PA employs a reconfigurable transformer in the input matching network to achieve low reflection coefficient across both bands, demonstrating significant flexibility in the design of dual-band power amplifiers with high output powers. Additionally, a detailed design methodology for the dual-band matching network is introduced. By utilizing this methodology, the PA has been designed using 55 nm CMOS technology. For continuous-wave operation, the PA achieves a saturated power ($P_{sat}$) of 28.03 dBm and 27.5–28.2 dBm, with power-added efficiency (PAE) of 33.2% and 24.6–31.1%, in the 2.4 GHz and 5 GHz WLAN bands, respectively. Concurrently, the PA power cells, which employ multi-gate transistor (MGTR) technology, achieve an intermodulation distortion (IMD3) of below 30 dBc at an output power of 15 dBm in both the 2.4 GHz and 5 GHz WLAN bands. The proposed PA outperforms other dual-band or multi-band PAs in terms of output power and exhibits great potential for WLAN applications.

In this paper, a dual-mode step-down DC-DC converter with an automatic mode-switching circuit is implemented in a 28 nm digital CMOS process and embedded in an RF transceiver chip to power the digital part. The proposed automatic mode-switching circuit includes a frequency-voltage conversion circuit that is designed according to the principle of charge redistribution on capacitance. The converter can switch modes according to the load without external intervention. This converter, along with a PMU sequencer, can also provide a solution for low-power design for system-on-chip applications. The IC occupies a total die area of 0.378 mm². The input voltage of the converter is 3.3 V, the output voltage is 1.05 V, and the maximum load current can reach 1 A. The converter shows a conversion efficiency of not less than 81% at a full load range and can achieve a peak conversion efficiency of 91% when the load current is 100 mA. The load range of the PWM mode is 1 A to 50 mA, and that of the PFM mode is 100 mA to 1 mA. The combination of zero-crossing detection circuitry and freewheel switches can reduce energy loss and eliminate additional electromagnetic interference.