American Journal of Electrical and Electronic Engineering, 2015, Vol. 3, No. 1, 1-3 Available online at http://pubs.sciepub.com/ajeee/3/1/1 © Science and Education Publishing DOI:10.12691/ajeee-3-1-1 New Very Low Frequency Oscillator Using only a Single CFOA D. K. Srivastava 1 , V. K. Singh 1,* , R. Senani 2 1 Electronics Engineering Department, Institute of Engineering and Technology, Lucknow, 226021 India 2 Division of Electronics and Communication Engineering, NetajiSubhas Institute of Technology, Sector 3, Dwarka, New Delhi, 110078, India *Corresponding author: vksingh@ietlucknow.edu Received December 19, 2014; Revised January 22, 2015; Accepted January 25, 2015 Abstract Some time back, Elwakil presented a systematic method of realizing Very Low frequency (VLF) oscillators using current feedback operational amplifiers (CFOA) and demonstrated that the classical Wienbridge oscillator, employing the concept of composite resistor (containing two positive and one negative resistance) can be tailored to generate VLF oscillations. The circuit proposed by Elwakil, however, required two CFOAs along with six resistors and two capacitors. The object of this paper is to report a new VLF oscillator circuit which, in contrast to Elwakil’s circuit, requires onlya single CFOA. The workability of the new circuit has been demonstrated by experimental results using commercially available AD844type CFOAs. Keywords: Oscillators, Current-feedback-operational amplifiers, current-mode circuits, single element controlled oscillators, very low-frequency oscillators Cite This Article: D. K. Srivastava, V. K. Singh, and R. Senani, “New Very Low Frequency Oscillator Using only a Single CFOA.” American Journal of Electrical and Electronic Engineering, vol. 3, no. 1 (2015): 1-3. doi: 10.12691/ajeee-3-1-1. 1. Introduction Very low frequency (VLF) oscillators (capable of generating frequencies < 20Hz) are required in many applications such as bio-medical instrumentation, geo- physical instrumentation and in some measurements in control system applications. Owing to the well-known advantages of current feedback op-amps (CFOA) (for instance, see [1,2,3,4]) and their wide spread acceptability as alternative building blocks, there have been numerous studies in recent literature on realizing sinusoidal oscillators using CFOAs, for instance, see [5,6,7,8] and references cited therein. In [8], Elwakil had reported a systematic method of designing VLF oscillators using CFOAs. The circuit of [8], however, requires two CFOAs along with six resistors and two capacitors (one of which is floating). The main object of this paper is to introduce a new CFOA-based VLF oscillator, which, by contrast to the circuit of [8], requires no more than a single CFOA and employs both grounded capacitors, as preferred for integrated circuit implementation. 2. Proposed VLF oscillator using a single CFOA CFOA is a four terminal building block which internally contains a plus type second generation current conveyor [9] and a voltage follower and is characterized by the following terminal equations y x y z x w i 0, v v , i i , v v = = = = z (1) The symbolic notation of the CFOA and its equivalent circuit are shown in Figure 1. Figure 1. Symbolic notation and the equivalent circuit of the CFOA C R C 4 C 4 3 y x 0 R 0 z w R 2 R 1 Figure 2. The proposed VLF oscillator The proposed circuit configuration is shown in Figure 2. Using equation (1) for the CFOA, a straight forward analysis of the circuit gives the condition of oscillation as