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This paper reports two new circuit topologies using second-generation current conveyors (CCIIs) for realizing variable frequency sinusoidal oscillators with minimum passive components. The proposed topologies in this paper provide new realizations of resistance-controlled and capacitor-controlled variable frequency oscillators (VFOs) using only four passive components. The first topology employs three CCIIs, while the second topology employs two CCIIs. The second topology provides an advantageous feature of frequency tuning through two grounded elements. Application of the proposed circuits as a wide-frequency range digitally controlled sinusoid generator is exhibited wherein the digital frequency control has been enabled by replacing both the capacitors by two identical variable binary capacitor banks tunable by means of the same binary code. SPICE simulations of the CMOS implementation of the oscillators using 0.35

Sinusoidal oscillators are very important analog circuits and find numerous applications in communication, control systems, signal processing, instrumentation, and measurement systems (see [

This paper reports two new topologies for oscillators using two/three CCIIs, four passive components, and which can realize oscillators with both Type1 and Type2 tuning laws (using RC-CR transformation), thereby adding to the current literature on active RC oscillators. The topologies can also provide quadrature current/voltage outputs because of the use of lossless integrators/differentiators. The resulting circuits are suitable for monolithic integration since both bipolar and CMOS implementations of CCII (both positive and negative) are available. CCII+ is available as a commercial IC (e.g., AD844 [

The first proposed circuit topology is shown in Figure

(a) First proposed circuit topology, (b) Type2 oscillator, and (c) Type1 oscillator.

The second proposed topology is shown in Figure

For Figure

(a) Second proposed circuit topology, (b) Type2 oscillator, and (c) Type1 oscillator.

Considering the nonidealities that arise from the actual physical implementation of the circuit, the characterizing equation of the CCII in (

The modified CO and FO for Type2 circuit, shown in Figure

The proposed circuits have been verified using SPICE simulations. Both the CMOS implementation of the oscillator using 0.35

Transistors widths for CCII.

MOSFET | |
---|---|

10/0.35 | |

6/1 | |

12/1 | |

12/1 | |

3/1 |

Possible (a) bipolar implementation of dual-output CCII− and (b) MOSFET implementation of complimentary output CCII.

Oscillator in Figure

Oscillator in Figure

Quadrature oscillator in Figure

Binary-weighted programmable capacitor bank.

(a) FO tuning, (b) amplitude variation, and (c) THD variation, with changing BC.

This paper reports two new CCII-based oscillator topologies that add to the current catalog of minimum passive component active-RC oscillators. A new topology with grounded frequency tuning elements is presented, and oscillators with frequency control via both resistor and capacitor are realized using the proposed topologies. SPICE simulation results using both the bipolar and CMOS implementation of the circuits have verified their workability. Application of the proposed circuit as a wide-frequency range digitally controlled sinusoid generator is also demonstrated.

The author would like to thank the anonymous reviewers for useful suggestions and comments, which helped to improve the paper substantially. The author is also grateful to Dr. Ali Umit Keskin, the associate editor of Active and Passive Electronic Components Journal, for enabling the prompt review of the paper. Part of this work was done while the author was with the Division of Electronics and Communications, Netaji Subhas Institute of Technology, University of Delhi, Delhi, India.