Analysis and Design of Front-end Amplifier Circuits Utilizing Feedback Techniques for Communication Systems

The aim of this dissertation is to develop some essential building blocks in wireless and wireline receiver analog front-ends, namely the low noise amplifier (LNA) and the transimpedance amplifier (TIA) with limiting post amplifier (PA).
Almost in any communication systems, amplifier plays critical role in order to boost the desired signal power, reduce the effect of in-band noise and achieve impedance matching. In a wireless communication system, the LNA is widely employed as the first stage amplifier of the front-end of receiver to provide sufficient gain for amplifying an input signal while maintaining low noise performance.
Therefore, in this dissertation, circuit designs of two CMOS LNAs are developed. One employs positive feedback technique to operate at microwatt power consumption for ISM band (5.8 GHz) applications; the other achieves broadband input matching and high power gain without inductive peaking technique for ultra-wideband (UWB) applications. Besides, the circuit analysis and design considerations of these LNAs are described in detail and the experimental results demonstrate a good figure of merit (FOM).
Being an essential component in the receiver front-end of an optical communication system, a TIA is widely utilized as the first building block to convert the weak current signal from the photodiode into a voltage signal. However, the
output swing of the TIA does not provide adequate voltage levels. Therefore, following the TIA, a high voltage gain amplifier is needed to further boost the output voltage swings of the TIA. In order to efficiently reduce the circuit area, a single-ended-to-differential (S2D) TIA followed by a limiting PA is presented without any on-chip inductors. The circuit analysis and design considerations of the inductorless TIA and limiting PA are also presented in detail. The fabricated inductorless TIA with limiting PA exhibits a transimpedance gain of 59 dBΩ and a wide -3dB bandwidth of 9.7 GHz. Therefore, it is still sufficient to operate at 12.5-Gb/s data rate.