Analog Integrated Circuits and Signal Processing

, Volume 81, Issue 1, pp 109–120 | Cite as

Design of positive feedback driven current-mode amplifiers Z-Copy CDBA and CDTA, and filter applications

  • Ersin Alaybeyoğlu
  • Arda Güney
  • Mustafa Altun
  • Hakan Kuntman


In this study, high-performance current-mode amplifiers Z-Copy current differencing buffered amplifier (ZC-CDBA) and current differencing trans-conductance amplifier (ZC-CDTA) are designed. In order to improve input impedances of the amplifiers, a new approach based on positive feedback is proposed. Impedance improvement/reduction is achieved by using only two extra transistors for each input. This number of extra transistors is very few compared to that in conventional negative feedback based improvement techniques. The proposed technique is justified by performing a detailed stability analysis. It is shown that the input impedances of ZC-CDBA and ZC-CDTA can be safely reduced to the level of 50 Ω by considering fabrication scatterings. The proposed amplifiers are verified with analog filter applications, a new KHN and recently proposed biquadratic and frequency agile filters. It is shown that the filters operate accurately at the frequency level of 100 MHz. This is a clear sign of the proposed amplifiers’ high performance. Layout and post layout simulations are done for the proposed circuits using AMS 0.18 µm parameters in Cadence environment.


Positive feedback CMOS integrated circuits Active filters Current-mode circuits 


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Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  • Ersin Alaybeyoğlu
    • 1
  • Arda Güney
    • 2
  • Mustafa Altun
    • 1
  • Hakan Kuntman
    • 1
  1. 1.Department of Electronics and Communication EngineeringIstanbul Technical UniversityIstanbulTurkey
  2. 2.Department of Electronics and Communication EngineeringYildiz Technical UniversityIstanbulTurkey

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