The authors present a new versatile circuit building block called a differential difference current conveyor (DDCC). An IC technique for implementing the DDCC is also presented. The DDCC-based frequency-selective circuits and nonlinear building blocks such as multiplier, squarer and square rooter are developed. Experimental results are given to demonstrate the feasibility of the proposed techniques, and they show that DDCC-based circuits offer a competitive design choice to CCIIbased and DDA-based circuits.

The Letter describes the design of a versatile analogue building block, termed an operational transresistance amplifier (OTRA). An operational transresistance amplifier has two low-input-impedance terminals and one low-output-impedance terminal. It is found to have a constant bandwidth independent of the gain in most closed-loop configurations. Simulation results are presented to demonstrate the constant-bandwidth performance. As an application example, this amplifier is used to implement a MOSFET-C differentiator, of which analysis and simulation results are also presented.

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Aparasitic-capacitance-insensitive MOS-FET-C integrator and differentiator using operational transresistance amplifiers are proposed and experimental results demonstrated. The bandwidths of these circuits are also independent of their gains. The required capacitances are smaller than those in previous work. Two new configurations of universal current-mode biquad filters based on these circuits are presented. A secondorder bandpass filter constructed using universal biquad filters and another third-order Chebyshev lowpass filter with 0.1 dB passband ripple are breadboarded and the measured results presented.

References prediction* from the above cited parameters and an assumed amplifier excess spontaneous emission factor of 1.4.We report two sets of BER measurements in Fig. 2. The first, carried out with the loop exactly as described above, and , , ' -1 0 1: