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

Ersin Alaybeyoğlu*, Arda Güney, Mustafa Altun, Hakan Kuntman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)109-120
Number of pages12
JournalAnalog Integrated Circuits and Signal Processing
Issue number1
Publication statusPublished - 23 Sept 2014

Bibliographical note

Publisher Copyright:
© 2014, Springer Science+Business Media New York.


  • Active filters
  • CMOS integrated circuits
  • Current-mode circuits
  • Positive feedback


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