An ultra high-speed and low-voltage amplifier for switched-capacitor applications

This paper propose a suitable structure to increase the gain and speed of low-voltage amplifiers by means of modifying the first stage of the Folded-Cascode (FC) structure and exploiting class AB amplifier with active load at the second stage. In spite of the fact that cascode structures increase the output impedance, we make an extra pole in the transfer function of the network to raise the transconductance of the whole circuit effectively. Moreover, the transistor of the active load current source operates like a common source amplifier. In order to improve phase margin, we utilize Feed-Forward (FF) compensation. Since we utilize cascode compensation at the second stage, the speed of the amplifier depends on only the first stage. This circuit is simulated with a 1.2 v single supply voltage in 0.13 mum process and Level49 (TSMC) parameters for 2 pf capacitor load. Finally, this structure is checked by a typical switched-capacitor integrator with a 100 MHz clock frequency. The results determined from simulation illustrate appropriateness of our solution in comparison with previous circuits.