Voltage Mode Astable Multivibrator Using Single CDBA

This paper aims at presenting three voltage mode square wave generator circuits using single current differencing buffered amplifier (CDBA), a recently proposed mixed mode building block. The first proposed circuit produces a variable frequency output having fixed duty cycle, whereas the rest of the circuits have variable duty cycle. One of the circuits uses passive element adjustment to control the duty cycle, whereas electronic control is used in the other circuit. The workability of the proposed circuits is confirmed through SPICE simulations and experimental work. 1. Introduction It is well known that inherent wide bandwidth which is virtually independent of closed loop gain, greater linearity and large dynamic range [1] are the key performance features of current mode technique. The CDBA is one such active element which exploits these advantages. In addition, it is free from parasitic capacitances [2] and, hence, is appropriate for high frequency operation. It provides further flexibility to the designers, enabling a variety of circuit designs, as it can operate in both current and voltage modes [3]. The square wave generator finds extensive applications in communication systems, control systems, instrumentation, and signal processing. The literature review reveals that several triangular/square wave generators using various analog building blocks have already been presented [4–11]. All these designs use a current source to alternately charge and discharge a capacitor followed by a Schmitt trigger to generate triangular/square wave. Conventional voltage-mode square wave generators [4] employ an op-amp working in the nonlinear region to produce a square wave signal. These voltage-mode generators, however, have a limitation on their maximum frequency due to lower slew rate and constant gain-bandwidth product of the op-amps. Triangular/square wave generators presented in [5–11] use current mode building-blocks-based circuits. The study of these circuits reveals that (i)references [5, 6, 10] employ more than one active element;(ii)references [6–10] use four or more passive elements;(iii)references [6–11] lack electronic controllability of duty cycle of output. The aim of this paper is to present three square wave generator circuits using single CDBA and three to five passive elements. In Section 2, the function of a CDBA is introduced followed by the description of proposed circuits with analytical formulation for the frequency of oscillation. Section 3 explores the effect of nonidealities of CDBA on the proposed circuits. PSPICE simulation results and