The commercialization of Ultra-WideBand (UWB) ranging from 3.1-10.6 GHz by Federal Communication Commission (FCC) has recently emerged as a promising technology for short-range wireless data communications. The applications of wireless data communications are RF Tag, wireless sensor networks, and Wireless Body Area Network (WBAN). According to the trend, the use of low-voltage, low-power, and Ultra-High Frequency (UHF) circuits and systems are immense and endless.
In this research work, two low-voltage and low-power Pseudo Differential (PD) Operational Transconductance Amplifiers (OTAs) are proposed for the design of UHF low-pass filter. UHF Low-pass filter is one of the basic blocks in the design of UWB Transceiver for UWB WPAN applications like radar, sensor networks, and RF Tag, etc. So, pseudo differential OTA has been used as a basic building block for UHF filters and for variable gain amplifiers, since it avoids the voltage drop across the tail current source. Generally, OTA dominates the total linearity characteristic of the filter. The design of low-voltage, low-power, and high frequency OTA with high linearity is very difficult. Various efforts to design a low-voltage, low-power, and high frequency OTA have been developed. According to the trend, in this paper two operational pseudo differential OTAs are proposed and implemented in UHF OTA-C filter design as an application.
There are several methods to design a low-voltage and low-power consumption pseudo differential OTA for UHF low-pass filter. One way to improve the frequency response of the filter is by increasing the transconductance of the OTA. In this work two pseudo differential inverter based symmetric CMOS pseudo differential OTAs have been proposed. One of the pseudo differential OTAs uses feedforward regulated cascode topology as a linearity improvement technique for UHF OTA-C filter design. Its input transistors are kept in triode region to guarantee the linearity. The drain voltages of the OTA's input transistors are also kept constant by using feedforward regulated cascode topology to improve the linearity. In the second proposed pseudo differential OTA, a simple external linearity improvement method has been used to minimize the number of non-dominant poles associated in first proposed OTA's regulation process. Also, the input transistors of the second proposed OTA are kept in triode region and their drain voltages are kept constant using external linearity improvement technique to improve the linearity. An efficient common-mode control circuitry has been used in both the OTAs to control the common-mode signal response. Simulation results show the first and the second proposed OTAs have a unity gain bandwidth of 800 $\It{MHz}$, and 1.2 $\It{GHz}$, respectively. They have a transconductance of 2.5 $\It{mS}$ with an IIP3 of 5.2 $\It{dBm}$, and 2.15 $\It{mS}$ with an IIP3 of 7 $\It{dBm}$. The power consumption of both the proposed OTAs is 1.1 $\It{mW}$. These proposed OTAs are implemented in a $9^{th}$-order 400 $\It{MHz}$ Chebyshev I low-pass filter as an application by using 0.13 $\It{\mum}$ technology. These filters have an attenuation of 30 dB at 600 $\It{MHz}$ by consuming only 13 $\It{mW}$.
