SIMPLE YET ACCURATE CURRENT COPIERS FOR LOW-VOLTAGE CURRENT-MODE SIGNAL-PROCESSING APPLICATIONS

As pressures increase on VLSI designers to use a lower supply voltage of 3.3 V rather than the present 5 V, current-mode signal-processing techniques will surely become increasingly important and attractive. Numerous current copiers have been proposed. Among them, the copier with a negative feedback approach is the best candidate for low-voltage current-mode signal-processing applications. However, the copier using a positive-gain feedback amplifier achieves better accuracy at the cost of increasing circuit complexity and settling time. This paper presents an alternative circuit implementation of the negative feedback approach. The proposed current copier uses a negative-gain feedback amplifier which can be easily realized by a simple circuitry with high accuracy and faster settling time. Simulation results show that with the simple digital CMOS process the proposed copier can be realized with only three transistors, achieves a dynamic range from 300 to 550 mu A with an accuracy of 0.1% and can be sealed within 3 ns with a power supply of 3.3 V. Thus the copier is well suited to our low-voltage current-mode sensor array applications.