CMOS HIGH-SPEED, HIGH-PRECISION CURRENT CONVEYOR AND CURRENT FEEDBACK-AMPLIFIER STRUCTURES

Most current mode circuits presented so far have been realized in bipolar technology. The most prominent family of bipolar current mode circuits is the current feedback operational amplifier which is now available as a standard device from many of the semiconductor manufacturers specializing in analogue circuits. However, when integrating VLSI systems CMOS is normally the preferred technology and hence CMOS implementations of analogue functions, including current mode functions, is attracting widespread interest. In the present paper we examine CMOS versions of some fundamental current mode analogue circuit blocks (current conveyors) and show how each of the basic blocks have significant drawbacks, especially with respect to precision, compared to their bipolar counterparts. It is further shown how a combination of a few basic building blocks can yield current mode functions (conveyors and current feedback amplifiers) with a significantly improved performance. Experimental results from an integration of the proposed CMOS current conveyor structures are given to confirm the conclusions reached through the theoretical investigations.