High performance electronically tunable log-domain current-mode PID controller Pipat Prommee a, * , Krit Angkeaw b a Department of Telecommunications Engineering, Faculty of Engineering, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520, Thailand b Instrumentation and Electronics Engineering Department, Faculty of Engineering, King Mongkut's University of Technology North Bangkok, Bangkok 10800, Thailand ARTICLE INFO Keywords: Control system Programmable controller PID Log-domain filters High-speed integrated circuit ABSTRACT This research proposes a log-domain P (proportional) I (integral) D (derivative) controller whereby the bias currents are arbitrarily applied to the P, I and D components for independent or simultaneous electronic tuning and the subsequent improved response. In the study, the initial P, I and D circuits were individually realized using 17, 13 and 21 bipolar transistors, and the final PID controller required 62 bipolar transistors including the biasing circuits and a multiple-output current buffer. The proposed PID controller was operational on a dual power supply of ±1.5 V, with the wide-range tunability up to three decades without the circuit topology alteration. Addi- tionally, simulations were carried out with the individual P, I, D circuits and PID controller to verify the per- formance (i.e. tunability and the response time) and the simulation results compared with the existing PID schemes. Importantly, the simulation results of the PID controller are in good agreement with the theoretical PID functions. 1. Introduction The Proportional-Integral-Derivative (PID) controller is a closed-loop controller that is commonly deployed in the industry sector, especially in the automatic process control applications, including the flow, temper- ature, pressure control [1,2]. The main advantage of the PID controller is the adjustability of the parameters to the specific plant [3,4]. In Ref. [5], the voltage-mode PID controller was realized using the operational amplifiers (OPAMPs) and passive elements. However, the OPAMP-based PID was limited in functionality and lacked the electronic tunability. More recently, several voltage-mode PID configurations were proposed based on the active building blocks (ABB), including the 2nd-generation current conveyors (CCIIs) [6–8], the operational trans- conductance amplifiers (OTAs) [9], and the current differencing buffered amplifiers (CDBAs) [10]. In Refs. [11,12], the voltage-mode PID circuits were realized using a single active element but the controllers lacked the tunable capability. In fact, the circuit construction with active building blocks necessitates numerous transistors, resulting in the bandwidth limitation. Furthermore, the PID circuits required the floating passive elements [6–8,10–12], giving rise to the integration challenges. Gener- ally, the voltage-mode integrated circuits are plagued with the following drawbacks: high voltage, high power consumption, slow response and a large die area. Specifically, the PID controllers based on CCIIs [6–8] were proposed, but they neither possessed the electronic tunable capability nor allowed for the independent controller-type selection (PID, PI, PD, P or I), in addition to the passive component-matching condition requirement. In Ref. [9], the OTA-based PID controller with two grounded capacitors and eight OTAs suffered from the multiple active components and limited bias-current tunability. In Refs. [13–17], the PID controllers were real- ized using the inverse band pass filters; however, the controllers lacked the electronic tunable capability and inhibited the independent controller-type selection. Moreover, the inverse filters required multiple active components. In Ref. [18], the cascode OTA-based PID was pro- posed using only 24 MOS transistors; however, the PID suffered from the PMOS and NMOS transistors mismatch, rendering it impractical to use. Moreover, the OTA contributed to the limited tunable range. In Ref. [19], the log-domain companding concept was introduced for the filter applications whereby the linear signal was systematically compressed into the nonlinear-domain compressed signal which pro- cessed in very low amplitude but higher than the noise floor prior to re-expanding to the linear signal, using the translinear principle [20]. In Ref. [21], the arbitrary-order log-domain filters were synthesized based on a state-space approach [21]. Due to the minimal of compressed signal, the process of charge and discharge capacitors become faster than linear-domain. More importantly, in comparison with the linear-domain * Corresponding author. E-mail addresses: pipat@telecom.kmitl.ac.th (P. Prommee), krita@kmutnb.ac.th (K. Angkeaw). Contents lists available at ScienceDirect Microelectronics Journal journal homepage: www.elsevier.com/locate/mejo https://doi.org/10.1016/j.mejo.2017.09.008 Received 12 May 2017; Received in revised form 11 July 2017; Accepted 27 September 2017 Available online xxxx 0026-2692/© 2017 Elsevier Ltd. All rights reserved. Microelectronics Journal xxx (2017) 1–12 Please cite this article in press as: P. Prommee, K. Angkeaw, High performance electronically tunable log-domain current-mode PID controller, Microelectronics Journal (2017), https://doi.org/10.1016/j.mejo.2017.09.008