New OTRA-Based Generalized Impedance Simulator

Operational transresistance amplifier (OTRA) has attracted considerable attention in the recent literature in several applications such as impedance simulation, universal biquad filter realization, realization of sinusoidal oscillators and multivibrators. However, to the best knowledge of the authors, any OTRA-based generalized impedance simulator circuits have not been reported so far. The purpose of this paper is to present such a circuit. 1. Introduction Although a large number of building blocks have been considered as an alternative to the classical voltage-mode operational amplifier (VOA) which suffers from the well-known disadvantage of gain-bandwidth conflict, the OTRA introduced in [1, 2] has been found to be particularly attractive in analog signal processing/signal generation due to the following advantageous features: transmission properties similar to the current feedback op-amp, lack of slew rate limitations as encountered in VOAs, and having two low-impedance inputs and one low-impedance output. The OTRA is a three-terminal analog building block defined by the following matrix equation: The circuit symbol of the OTRA is shown in Figure 1. In an OTRA, both input terminals are virtually grounded, and the output voltage is the difference between the two input currents multiplied by the transresistance gain , such that Figure 1: Circuit symbol of the OTRA. Thus, both input and output terminals are characterized by low impedance, thereby eliminating response limitations incurred by capacitive time constants leading to circuits that are insensitive to the stray capacitances at the input terminals. For ideal operation, the transresistance gain approaches infinity forcing the input currents to be equal. Thus, the OTRA is employed in a negative feedback configuration in a way similar to the operational amplifiers. For discrete designs, the OTRA can be implemented using two current feedback operational amplifiers (CFOA) (see [3–5], and references cited therein) as shown in Figure 2. On the other hand, from the viewpoint of analog VLSI implementation, several high-performance CMOS OTRA realizations have also been introduced in the current literature for instance, see [1, 6, 7] and the references cited therein. An exemplary CMOS implementation from [6] is shown in Figure 3. The use of OTRAs has been widely investigated in a number of applications such as immitance simulators [3, 5, 8, 9], integrators [10], filters [11–22], square-wave generators [23], current-mode monostable multivibrators [24] and oscillators [4, 25, 26], to name a few. Figure 2: