Tham khảo tài liệu 'advances in solid state part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 5 Low-Voltage Fully Differential CMOS Switched-Capacitor Amplifiers Tsung-Sum Lee National Yunlin University of Science and Technology Taiwan . 1. Introduction Analog signal amplification in discrete-time system can be performed by switched-capacitor amplifiers Martin et al. 1987 . Switched-capacitor amplifier has been used in the design of digital-to-analog converter Yang Martin 1989 . The schematic for the switched-capacitor amplifier is shown in Figure 1. Fig. 1. A differential-to-single-ended CMOS switched-capacitor amplifier. Depending on the input-stage clock signals the amplifier can be either noninverting as shown or inverting input-stage clocks shown in parentheses . 82 Advances in Solid State Circuits Technologies Assuming an infinite op amp gain the output voltage at end of Ộ2 is given by C T Vout nT C1 Vm nT - T 1 irrespective of the op amp offset voltage. If the clock waveforms shown in parentheses are used then an inverting function is realized and . . C . . Vout nT - C- Vm nT 2 C2 again independent of the op amp input offset voltage. During the reset phase Ộ1 C3 is connected in feedback around the op amp which causes the output change only by the op amp input offset voltage. The switches are realized as CMOS transmission gate. For low supply voltages a conductance gap begins to appear around the middle of the supply range Crols Steyaert 1994 . This means that under low-voltage operation this configuration no longer works. Existing solutions of low-voltage operation of switched-capacitor circuits include using low threshold voltage process Matsuya Yamada 1994 switched-opamp technique Baschirotto Castello 1997 Cheung et al. 2001 Cheung et al. 2002 Cheung et al. 2003 Crols Steyaert 1994 Peluso et al. 1997 Peluso et al. 1998 Sauerbrey et al. 2002 Waltari Halonen 2001 Wu et al. 2007 opamp-reset switching technique Chang Moon 2003 Keskin et al. 2002 Wang . Embabi 2003 voltage multiplier charge pump technique Nicollini et al. 1996 Rombouts et al. 2001
