Inyoung Choi

Accurate dB-Linear Variable Gain Amplifier With Gain Error Compensation

This paper describes use of a novel exponential approximation for designing dB-linear variable gain amplifiers (VGAs). The exponential function is accurately generated using a simple error-compensation technique. The dB-linear gain is controlled linearly by the gate voltage, resulting in a simple and robust VGA. The proposed dB-linear VGA fabricated in a 65-nm CMOS process achieves a total variable gain range of 76 dB and dB-linear range greater than 50 dB with ±0.5-dB gain error. Under a 1.2-V supply voltage, the current consumption of the VGA is 1.8 mA and that of the output buffer is 1.4 mA. The input-referred in-band noise density is 3.5 nV/√{Hz} and the in-band OIP3 is 11.5 dBm. Due to the very simple circuit topology, the total active area of the VGA and the output buffer is extremely small, 0.01 mm2.

Wideband LNA Using a Negative gm Cell for Improvement of Linearity and Noise Figure

A differential common gate low noise amplifier (LNA) has been widely used for a wideband LNA. However, it has poor linearity due to a nonlinear transconductance in a MOSFET and poor noise performances from the common gate configuration. We propose a differential common gate LNA with a negative g m cell for the improvement of the linearity and noise figure. The cell comprises cross coupled transistors instead of a current source. The negative g m cell creates the opposite phased harmonic, canceling the distortion. The noise figure is improved by canceling the noise from the common gate transistors through the negative g m cell. The LNA is fabricated in 0.13 μm RF CMOS. The LNA has the bandwidth of 0.7 ∼ 3.5 GHz frequency and has provided the expected characteristics for linearity and noise figure.

A Wideband Differential Low-Noise-Amplifier With IM3 Harmonics and Noise Canceling

This letter presents a wideband 2-stage differential LNA which utilizes the canceling techniques of IM3 harmonic distortion and noise. The 1st stage adopts a gm-boosted cross-coupled push-pull amplifier to achieve an input matching and reduce the NF. The 2nd stage simultaneously cancels the IM3 and thermal noise of the transistors in the 1st stage. The LNA has a gain of 16~18 dB in a wide bandwidth of 0.1~2.5 GHz, while consuming 13 mW from a 1.2 V power supply. The NF is 1.7~2.7 dB and IIP3/IIP2 are -3 ~ 0/18~21.5 dBm, respectively. The LNA is fabricated in 65 nm digital CMOS technology and the chip area is 0.008 mm2.

A Wideband Digital RF Receiver Front-End Employing a New Discrete-Time Filter for m-WiMAX

A wideband digital RF receiver front-end employing a discrete-time (DT) filter is presented for application to m-WiMAX (WiBro). By employing a sampling mixer and a DT filter, the receiver operates in the charge domain. In addition to the flexibility of the DT filter, the new non-decimation finite impulse response (NDF) filter can be cascaded to a conventional finite impulse response (FIR) filter without the decimation effect. Thus, we can easily increase the order of the sincn function-type filtering response and the signal processing bandwidth. The FIR filter is also modified to reduce the noise and the number of required clock signal. Because of the new filter configuration, clock signals can be shared by the FIR filter and NDF filter and the clock generator circuit can be simplified. The designed receiver front-end is implemented using an IBM 0.13-μm RF CMOS process. The fabricated chip satisfies the m-WiMAX specification of an 8.75 MHz channel bandwidth and the total system current dissipation is 26.63 mA from a 1.5-V supply voltage.

A Sub-mW Fully Integrated Wide-Band Receiver for Wireless Sensor Network

This letter presents low power implementation of a fully integrated wide band receiver for wireless sensor network. The receiver targets extremely low power operation with wide band coverage. Fabricated in 28 nm CMOS process, the receiver employs a passive mixer-first RF front-end with zero-IF architecture which is driven by non-overlapping four-phase local oscillator (LO). To minimize power consumption in LO driving stage which consumes the largest portion of power in this structure, supply voltage and device size optimization techniques are introduced. Enhanced non-overlapping LO circuit is proposed to prevent degradation of the noise figure. The receiver also includes a low power base band amplifier and in-band noise reduced biquad filter. The total receiver chain achieves conversion gain of 55 dB, noise figure of 13.6 dB and IIP3 of -7.5 dBm (@10 MHz spacing) with power consumption under 1 mW at the frequency band of 0.85 ~ 2.55 GHz.

A passive mixer-first receiver front-end without external components for mobile TV applications

This paper describes a passive mixer-first receiver front-end (RFE) for mobile TV covering 100MHz to 800MHz without any external components. The proposed input matching technique with RC discharging circuit achieves a simple topology with a low noise. The out-of-band linearity is enhanced using the low pass filtering of sampling capacitor, delivering an outstanding out-of-band linearity. The out-of-band IIP3 and IIP2 are 7dBm and 36dBm, respectively at the maximum gain setting of 36dB. The third and fifth harmonic rejection ratios (HRR) are 49dB and 42dB, respectively. The power consumption is 23mW and the maximum NF is 3.6dB. The active area occupies 0.33mm2 in 65nm CMOS technology.

Digital RF receiver front-end with wideband operation capability for m-WiMAX

A Digital RF receiver front-end with wideband operation capability is presented for m-WiMAX application. By employing sampling mixer and discrete-time filter, the receiver operates in charge domain. In addition to flexibility of the discrete-time (DT) filter, the new Non-Decimation Finite Impulse Response (FIR) filter can be cascaded to a conventional FIR filter. And we can easily increase the order of the sincn-type filtering response and achieve wideband signal process capability. The designed receiver front-end is implemented by IBM 0.13-µm RF CMOS process. The chip satisfies the m-WiMAX specification with 26.63mA from a 1.5-V supply voltage for the total system.

A wideband LNA with dual-feedback for TV tuner

A wideband LNA is the first amplifying stage in TV tuner system. It requires a low noise figure with a sufficient gain and a high linearity such as high IIP2 and IIP3 due to the many adjacent channels. This paper represents the wideband CMOS LNA using a dual feedback for the tuner application, which can suppress the second and the third order distortions with a low noise and a suitable gain. In the dual feedback, the weak negative feedback improves the linearity of the transconductance partially, thereby maintaining the high gain and low noise. The residual distortion and the distortion of the buffer are cancelled by the positive feedback. Consequently, the proposed wideband LNA with the dual feedback improves noise figure and linearity with a high gain. The LNA fabricated in 0.18 µm RF CMOS demonstrates the expected performances.