CMOS AMPLIFIER MODULE ALLOWING FOR VOLTAGE, CURRENT, TRANSIMPEDANCE AND TRANSADMITTANCE TRANSFER FUNCTIONS IMPLEMENTATIONS Md. A.H. Talukder and R. Raut Department of Electrical and Computer Engineering Concordia University 1455 DE Maisonneuve Blvd. West, Montreal, Canada, H3G 1M8 e-mail: m_talukd@encs.concordia.ca, rabinr@ece.concordia.ca Abstract— This article presents a universal amplifier module (UAM), implemented in 180 nm CMOS technology, that can be configured to function as a (i) voltage controlled voltage source (VCVS), (ii) current controlled current source (CCCS), (iii) voltage controlled current source (VCCS), (iv) current controlled voltage source (CCVS), and (v) current conveyor (type II). As a result, the amplifier can be used to produce four kinds of basic circuit transfer functions, i.e., voltage-, current-, transadmittance- and transimpedance- transfer functions. This is validated by presenting simulation results for a second order voltage, current, transadmittance and transimpedance bandpass filter (BPF) transfer functions using only three UAM devices. The device is expected to be useful in a complex VLSI system environment where interfacing between sub-systems with varied impedance levels is required. Keywords— Universal amplifier module (UAM), CMOS analog integrated circuits, Voltage and current mode signal processing, Transadmittance filter (TAF), Transimpedance filter (TIF). I. INTRODUCTION The Advent of CMOS technology has facilitated the invention of several analog amplifiers, such as operational amplifiers, operational transconductance amplifiers etc. [12]. These amplifiers have been used for both voltage and current mode signal processing. In the recent past people have introduced new circuit modules that can produce voltage and current mode transfer functions only [3-4]. In this article we report a UAM that can be configured as any one of the four basic electronic amplifiers (i.e., VCVS, VCCS, CCVS, CCCS) as well as a type II Current Conveyor (CCII). The UAM introduced by us can produce transadmittance-, and transimpedance- transfer functions, in addition to voltage and current-mode transfer functions. Thus it can be used to produce four kinds of transfer functions. In section II, the design principles of the proposed UAM with different sub-systems are discussed and principles of implementing the four basic amplifiers as well as a CCII with the UAM are described. In section III, several performance parameters measured by HSPICE simulation on the post layout extracted data file are presented. Section IV presents the configurations for realizing second-order band- pass filters as voltage-, transadmittance, curren- and transimpedance transfer functions using only three UAM devices. The response curves for all the four filter transfer functions are presented. Section V concludes the article. II. THE AMPLIFIER MODULE A. The circuit Figure 1 shows the schematic diagram of one-half of the fully differential UAM. The transistors M0-M3 provide the bias currents. We will discuss the system by considering the half-system comprised of transistors M17, MX4-MX23. Transistors M17, MX8, MX10 serve as current mirror bias sources. Corresponding transistors in the other half-system are labelled as MY4, MY5 ... and so on. The transistors MX4-MX7 depict the half-system of the differential voltageand current- input terminals of the fully differential system. Following the input stage, there are voltage level shifter stages with frequency compensation circuit (MX8-MX13), and a voltage output buffer circuit (MX14-MX16). A wideband transconductor (MX20-MX23) [5] serves as the output current buffer circuit. The pass transistor MX18 activated by the digital control signal D1 (1/0) facilitates the gate-drain connected transistors (MX6-MX7) to receive an input current signal for current-mode operations. Similarly, the pass transistor MX19 activated by the digital control signal D2 (0/1) can deliver the output either from the lowimpedance voltage buffer (for voltage or transimpedance amplifier operation), or from the high-impedance current buffer (for current or transadmittance amplifier operation). The digital control signals D1, D2 thus can configure the UAM for four-mode signal processing applications, i.e., (i) voltage, (ii) trans-admittance, (iii) current, and (iv) transimpedance transfer functions. B. Implementations of four basic amplifiers and a CCII The principles of configuring the UAM as four basic electronic amplifiers and a CCII are presented in table I. The 2012 25th IEEE Canadian Conference on Electrical and Computer Engineering (CCECE) 978-1-4673-1433-6/12/$31.00 ©2012 IEEE Figure 1: Schematic diagram of half circuit of the universal amplifier module (UAM) phases (ON or OFF) of the switches D1, D2 that are used to choose voltage or current signal to be applied at the input or sample the signals from the output buffer are also shown in the table. C. Layout data The UAM of Fig.1 has been laid out in 180 nm CMOS technology. The layout is connected with the pad frame and is ready for fabrication. Figure 2 shows the layout view of the UAM. Chip area of the UAM is 0.7 mm2 and it consumes 7.179 mW of power from ±1.3 V supply. Table II presents the dimensions of the transistors (M0-MX23) used in halfcircuit of the UAM. III. RESULTS A. Design validation Post layout simulations of the different sub-systems of the UAM using HSPICE provide similar results as the values predicted by appropriate theoretical formulae. The DA stage layout block provides gain of 55.34 whereas the theoretical gain is 56. The level shifter stages layout block provide gain of 126.5 and 133.93 respectively whereas theoretical values are 125.11 and 149 respectively. The voltage buffer stage provides gain of 0.84 whereas the theoretical gain is 0.73. B. Performance parameters Table III presents several important performance parameters of the UAM obtained by HSPICE simulations together with similar results reported by other researchers. In some cases, comparative work of other researchers can not cited since a device like the UAM has not been introduced in the past. IV. APPLICATION EXAMPLES A. Voltage mode filter (VTF) and transadmittance filter (TAF) implementation The proposed amplifier module can be used to implement identical (except for a multiplicative constant) voltage (VTF)- and transadmittance (TAF) mode 2nd order BPFs. Figure 3 presents the configuration for the band pass filters (VTF and TAF) using Ackerberg, Mossberg’s structure [6]. For the elements in Fig. 3, the transfer function is given by: 1 s I Vo1 RC1 (4.1) =− = o r 1 Vi Vi 2 1 s +s + R1C1 C1C 2 R2 rr2 From equation (4.1), it is seen that, the VTF (=Vo1/Vi) and the TAF (=Io/Vi) have the same form. The simulated frequency responses are shown in Fig. 4. Each of the filters has center frequency of fp = 10 KHz and pole-Q factor = 2.5. BPF response of VTF, TAF, CTF, TIF 80 VTF (dB) TAF (dBmho) CTF (dB) TIF (dBohm) 60 40 20 dB 0 -20 -40 -60 -80 -100 -120 1.E+00 1.E+01 1.E+02 1.E+03 frequency 1.E+04 1.E+05 1.E+06 Figure 4: Frequency response of band-pass VTF, TAF, CTF and TIF using three UAMs. Figure 2: Layout view of the universal amplifier module Configuration for the CTF and TIF are not shown here for lack of space. Frequency response of the CTF and TIF are included in Fig. 4. All the filters have same center frequency (10 KHz) and pole-Q factor (2.5). V. Figure 3: Implementation of band-pass VTF and TAF using the UAM B. Current mode filter (CTF) and transimpedance filter (TIF) implementation The proposed UAM can also be used to implement identical current-mode (CTF) and transimpedance (TIF) function filters. The transfer function is given by: Io =− I i1 s 1 RC1 r1 1 s2 + s + R1C1 C1C 2 R 2 rr2 = Vo I i1 (4.2) From equation (4.2), it is seen that, the CTF (=Io/Ii1) and the TIF (=Vo/Ii1) have the same form. The CTF is obtained directly from the VTF of Fig. 3 by just reversing the inputoutput ports of the each UAM device in the VTF and applying current signal at the transposed input port. This involves application of the principle of transposition [6]. CONCLUSIONS A universal amplifier module (UAM) in 180 nm CMOS technology has been proposed in this article. The UAM is configurable for either voltage or current mode signal processing by digitally controlled switches and can provide four types of transfer functions, i.e., voltage-, current-, transadmittance- and transimpedance- transfer functions. Several performance parameters of the proposed amplifier module obtained by HSPICE simulations on the post layout extracted data have been reported. Simulated responses of a second order voltage-mode (VTF), current-mode (CTF), transadmittance (TAF) and transimpedance (TIF) band-pass filter transfer functions using only three UAM devices are reported. The UAM will be a desirable active device for multi-mode signal processing in a complex system where interfacing between adjacent sub-systems with any one of four kinds of possible input/output impedance levels need be established optimally. ACKNOWLEDGEMENTS The work was supported by a research grant from the Natural Science and Engineering Research Council (NSERC), Canada, and a grant in support for research thesis (SRT) from the Faculty of Engineering and Computer Science, Concordia University, Montreal, Canada. REFERENCES [1] K. Khare, N. Khare and P.K. Sethiya, ‘Analysis of low voltage rail-torail CMOS operational amplifier design,’ International Conference on Electronic Design, 2008, December 1-3, Penang, Malaysia, pp. 1-4. [2] E. Sanchez-Sinencio and J. Silva-Martinez, ‘CMOS transconductance amplifiers, architectures and active filters: a tutorial,’ IEE Proceedings G – Circuits, Devices and Systems, 2000, February, vol. 147, issue 1, pp. 3-12. TABLE II: TABLE FOR DIMENSIONS OF THE TRANSISTORS IN THE HALF- [3] P. Lung Chu, and H. Pin Chen, ‘Versatile voltage-mode multifunction biquadratic filter employing DDCCs’, International Conference on SolidState and Integrated-Circuit Technology, 2008, October, pp. 1789-1793. [4] P. Mongkolwai, T. Pukkalanun, and W. Tangsrirat, ‘Current-mode universal biquad with orthogonal ωp-Q tuning using OTAs’, International Conference on Information, Communications & Signal processing, 2007, December, pp. 1-4. [5] R. Raut, ‘Wideband CMOS Transconductor for Analog VLSI Systems’, IEEE Transactions on Circuits and Systems II: Analog and Digital Signal Processing, 1996, November, vol. 43, issue 11, pp. 775–776. [6] R. Raut, M. N. S. Swamy, and Nong Tian, ‘Current-Mode Filters Using Voltage Amplifiers’, Circuits Systems and Signal Processing, 2007, September/October, vol. 26, issue 5, pp. 773-792. [7] K. J. de Langen, and J. H. Huijsing, ‘Compact low-voltage powerefficient operational amplifier cells for VLSI’, IEEE Journal of Solid-State Circuits, 1998, October, vol. 33, issue 10, pp. 1482-1496. [8] M. Abdulai and P. Kinget, ‘A 0.5 V Fully Differential Gate-input Operational Transconductance Amplifier with Intrinsic Common-Mode Rejection’, IEEE ISCAS 2006, May 21-24, Island of Kos, Greece, pp. 28372840. CIRCUIT OF THE PROPOSED AMPLIFIER MODULE TRANSISTORS W (µm) L (µm) M0, M1, MX15 20 1.2 M2, M3 10 1.2 MX4 40 1.2 MX5 23.4 1.2 MX6 74.2 1.2 MX7, MX12 13 1.2 M17 95 1.2 MX8 70 1.2 MX9 11.9 1.2 MX10 37 1.2 MX13 1 2.3 10.1 1 TABLE I: CONFIGURING THE UAM FOR FIVE DIFFERENT BUILDING BLOCKS Switching position Types of amplifier MX11 D1 = OFF, D2 = ON D1 = OFF, D2 = OFF D1 = ON, D2 = OFF D1 = ON, D2 = ON D1 = OFF, D2 = OFF VCVS VCCS CCCS CCVS CCII MX14 9 1.2 MX16 7.7 1.2 MX20 65 1.5 MX21 70 1.5 MX22, MX23 1.5 1.5 TABLE III: TABLE FOR PERFORMANCE PARAMETERS MEASUREMENT OF THE UAM TOGETHER WITH SIMILAR RESULTS REPORTED BY OTHERS Voltage Amplifier (VCVS) Transadmittance Amplifier (VCCS) This work Other [7] This work CMOS Technology 180 nm 160 nm Power supply ±1.3 V Parameters Other [8] Transimpedance Amplifier (CCVS) Current Amplifier (CCCS) 180 nm 180 nm 180 nm 180 nm 1.8V – 7V ±1.3 V 0.5 V ±1.3 V ±1.3 V Open loop Gain 117.8 dB 86 dB 7.22 dB A/V 55 dB 165.1 dBΩ 54.32 dB Unity gain BW 272.7 MHz 4 MHz 72.83 KHz 8.72 MHz 1.28 GHz 8.92 MHz Phase margin 56.90 670 64.40 610 53.50 44.120 Gain margin 49.86 dB - 68.83dB - 88.09 dB 58.76 dB Input offset -97.33 pV 6 mV -11.14 pV - 1.49 µA - Input CMR -690 mV ↔ +467.7 mV Vss –0.5V↔ Vdd – 1.3V -1.069 V ↔ +1.069 V - -0.4 mA ↔ +10 mA -10 mA ↔ +53.37 µA Output swing -117.9 mV ↔ 328.5 mV Vss + 0.1 V ↔Vdd–0.1V -1.025 µA ↔ -689.1 µA - -252 mV ↔ +1.048 V -1.054 mA ↔ +947.2 mA Slew rate 2.42 V/µs 4 V/µs 0.45 V/µs 1.35 V/µs 3.2 V/µs 0.22 V/µs CMRR 200.79 dB - 156.01 dB 61.9 dB 78.3 dB 83.17 dB PSRR 82.74 dB - 48.21 dB - 84.55 dB 87.93 dB Output offset 8.8 nV - 90 fA - -260.5 µV - Output resistance 1.1 KΩ - 115.62 KΩ 200 KΩ 1.1 KΩ 115.62 KΩ Input resistance ∞ - ∞ - 0.2 KΩ 0.2 KΩ Power dissipation 7.179 mW 9 mW 7.179 mW 77 µW 7.179 mW 7.179 mW