A New Current-Mode Log and Antilog Amplifier using Current Follower Transconductance Amplifier (CFTA)


  • Amira R Hamad Department of Electrical Engineering, College of Engineering, Salahaddin University-Erbil, Kurdistan Region, Iraq
  • Azad N Abdulla Department of Electrical Engineering, College of Engineering, Salahaddin University-Erbil, Kurdistan Region, Iraq




Log amplifier, antilog amplifier, CFTA, Current Mode


Log and Antilog Amplifiers are two very important functions in many electronic devices. Thus, in this article a new current mode (CM) log and antilog amplifier using current follower transconductance amplifier (CFTA) are presented. The logarithmic circuit is constructed using only one CFTA as active elements and one metal oxide semiconductor (MOS) transistor as diode operation and antilogarithmic amplifier circuit is implemented using only one CFTA as the active component, one MOS transistor as diode operation and two MOS transistor as active resistors. It provides the advantage of using MOS transistor instead of a resistor and diode that is beneficial to IC implementation in terms of space consideration which are suitable for IC implementation. These circuits provide logarithmic and antilogarithmic responses. Additionally, there is no demand to set selection criteria for components. The operation of the circuit in the current mode was verified by a non-ideality study. PSPICE was used to test the scheme's functioning. The output curves coincide very close with the theoretical expectation.


Başak, M.E. & Özer, E. 2022. Electronically tunable grounded inductance simulators and capacitor multipliers realization by using single Current Follower Transconductance Amplifier (CFTA). Analog Integr Circ Sig Process. 112, 401–415.

Chris, D. H., James, W. H., John, G. M. ,Douglas, B. R & Bergsma, A. J. 2002. A DC–4-GHz True Logarithmic Amplifier: Theory and Implementation. IEEE Journal of Solid-State Circuits. 37(10), 1290-1299.

Chen, J. S., & Ker, M. D. 2007. The impact of gate-oxide breakdown on common-source amplifiers with diode-connected active load in low-voltage CMOS processes. IEEE transactions on electron devices. 54(11), 2860-2870.‏

Daibor, B., raj, S., Viera, B., & Zdenek, K. 2008. Active Elements for Analog Signal Processing: Classification, Review and New Proposals. Radioengineering. 17(4), 15-32.

Indu, P., Meeti, D. & Kalyan S. 2013. Switched capacitor-based Log –Antilog Amplifier Using CDTA a Current mode implementation. International Journal of Electronics and Communication Engineering & Technology, 4(6), 21-28.

Mohammad , M. , Mishra, R. K., Muzaffar, A. S. & Pyari, M. P. 2012. CDTA Based Logarithmic Amplifier. IEEE International Conference on Signal Processing, Computing and Control, 1-4, Solan, India.

Neeta, P., Pragya, T., Rajeshwari, P. & Ravi, B. 2014. OFCC based Logarithmic Amplifier. International Conference on Signal Processing and Integrated Networks (SPIN), 522-525, Noida, India.

Nisha, W. & Syed, N. 2015. Realization of a New Current Mode Second Order Biquad Using Two Current Follower Transconductance Amplifiers (CFTAs). Circuits and Systems, 6(5), 113-120.

Pandey, R. & Pandey, N. 2018. OTRA Based Log and Antilog Amplifiers. 61st IEEE International Midwest Symposium on Circuits and Systems (MWSCAS), 182-185.

Harnsoongnoen, S., Sa-ngiamsak, C., & Silapunt, R. 2008, July. Logarithmic and antilogarithmic circuit with gate–to–substrate biasing technique. In ITC-CSCC: International Technical Conference on Circuits Systems, Computers and Communication,s 1069-1072.‏

Rout, S. S., Acharya, S., & Sethi, K. 2020. Design of a low power and low phase noise VCO using active resistor and DTMOS. In Advances in Electrical Control and Signal Systems: Select Proceedings of AECSS, 671-679. Springer Singapore

Surasak, I. & Ittipong, C. 2019. A Modified Current Differencing Buffered Amplifier and Its Application. 34th International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC), 1-4, JeJu, Korea (South).

Tangsrirat, W., Dumawipata, T., & Surakampontorn, W. 2007. Multiple-input single-output current-mode multifunction filter using current differencing transconductance amplifiers. AEU-International Journal of Electronics and Communications, 61(4), 209-214.‏




How to Cite

Hamad, A. R., & Abdulla, A. N. (2024). A New Current-Mode Log and Antilog Amplifier using Current Follower Transconductance Amplifier (CFTA). Zanco Journal of Pure and Applied Sciences, 36(3), 35–42. https://doi.org/10.21271/ZJPAS.36.3.5



Engineering and Computer Sciences