Design of high-speed high-accuracy current copiers for low-voltage analog signal processing applications

For high-accuracy current-mode circuits, their basic building blocks, current copiers, determine their speed and accuracy. A current copier suffers from two major error effects which are due to nonzero output conductance and clock feedthrough. This brief presents a simple current copier with a negative-feedback structure to alleviate the error due to nonzero output conductance, where the feedback amplifier is implemented by a bipolar inverter with high voltage gain and large bandwidth. This brief also presents the design constraints and trade-off for reducing the error due to the clock feedthrough. The PSPICE simulation results show that the copier achieves an accuracy of more than 10 b with a settling time within 6 ns for the input currents ranged from 0.5 to 3 mA, where a power supply of 3.3 V and a 2 μm BiCMOS process are assumed. Thus, this current copier is well suited to the high-accuracy high-speed and low-voltage analog signal processing applications