HO8_315aSP09_alt_integ

HO8_315aSP09_alt_integ - Alternative Integrator...

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Unformatted text preview: Alternative Integrator Implementations Parameter Tuning Boris Murmann Stanford University murmann@stanford.edu Copyright © 2009 by Boris Murmann B. Murmann EE315A ― HO #8 1 Outline • In the past several lectures, we have primarily employed active p , p y p y RC-Opamp integrators in our filter implementations • Today we’ll consider a number of alternative implementations that have found their use in practice – MOSFET-Opamp-C – Gm-OTA-C – Gm-C • In addition, we will look at methods that have been used to “tune” the time constants (and other p ( parameters) of various ) integrators toward their desired values B. Murmann EE315A ― HO #8 2 MOSFET-C Integrator C • MOSFET in triode used to replace resistor • Advantages – Continuous tuning mechanism for i t f integrator time constant t ti t t – Potentially cheaper fabrication process • Disadvantages – Large parasitics, distributed RC along channel – Bias point sensitivity – Weakly nonlinear R Vin Vout C VC Vin Vout ID = μCox 1 RMOS = W L VDS ⎞ ⎛ ⎜VGS − Vt − 2 ⎟VDS ⎝ ⎠ dID W = μCox (VGS − Vt − VDS ) dVDS L EE315A ― HO #8 B. Murmann 3 Czarnul Circuit Z. Czarnul, "Modification of Banu-Tsividis continuous-time continuous time integrator structure," Circuits structure and Systems, IEEE Trans. Ckt. Syst., pp. 714716, July 1986. • Mitigates bias point sensitivity and removes second harmonic distortion • Remaining issues – Backgate effect – Short channel effects Assuming Va = 0 (without loss of generality) ( ) ( ) W [VA − Vt ]Vin − Vin2 + [VC − Vt ] ( −Vin ) − Vin2 L W IO 2 = ID 3 + ID 4 = μCox [VC − Vt ]Vin − Vin2 + [VA − Vt ] ( −Vin ) − Vin2 L W IO1 − IO 2 = 2μCox [VA − VC ]Vin L IO1 = ID1 + ID 2 = μCox B. Murmann EE315A ― HO #8 4 Gm-Opamp-C Integrator • • C Vin - Gm Transconductor replaces resistor – Built e.g. using a differential p g g pair Advantages – Main amplifier sees only capacitive loads Vout • Can replace with “OTA” Iin = GmVin H (s ) ≅ − 1 R↔ Gm B. Murmann – Continuous tuning mechanism for integrator time constant Gm sC • E.g. via IBIAS of Gm cell – Potentially cheaper process • Disadvantages – Nonlinearity of Gm cell – Extra power dissipation EE315A ― HO #8 5 Example (1) C.A. Laber, P.R. Gray, "A 20-MHz sixth-order BiCMOS parasitic-insensitive continuoustime filter and second-order equalizer optimized for disk-drive read channels ," IEEE J. Solid-State Circuits, vol. 28, no. 4, pp.462-470, Apr. 1993. B. Murmann EE315A ― HO #8 6 Example (2) C.A. Laber, P.R. Gray, "A 20-MHz sixth-order BiCMOS parasitic-insensitive continuous-time filter d filt and second-order equalizer optimized f d d li ti i d for disk-drive read channels ," IEEE J. Solid-State Circuits, vol. 28, no. 4, pp.462-470, Apr. 1993. EE315A ― HO #8 B. Murmann 7 OpAmps versus OTAs (1) Operational Amplifier B. Murmann Operational Transconductance Amplifier EE315A ― HO #8 8 OpAmps versus OTAs (2) OpAmp OTA • Mostly used “on-chip” • "General Purpose" • High output impedance • Low output impedance – Ideally a voltage controlled voltage source – Ideally a voltage controlled current source • • Not well suited for resistive loads, mostly used to drive capacitive loads • Can drive resistive and capacitive loads • Essentially an OTA + buffer Usually lower (total integrated) noise – Buffer increases complexity and p y power dissipation EE315A ― HO #8 B. Murmann 9 Loading Considerations (1) ron||rop vo Single-ended OTA model vi RL CL • Low load resistance will "destroy" the gain of our amplifier – RL may be an explicit load or due to loading from the feedback network • But, we want large (loop) gain for good precision B. Murmann EE315A ― HO #8 10 Loading Considerations (2) ron||rop p vo 1 Single-ended OpAmp model vi RL CL • Adding a buffer allows us to drive resistive loads and still achieve high gain • But – Buffer can be difficult to build – Is costly in terms of headroom (e.g. source follower) – Add additional area, power Adds dditi l EE315A ― HO #8 B. Murmann 11 Loading Considerations (3) Single-ended model of a two-stage OTA • Resistive load "destroys" gain of second stage only – First stage sees capacitive load • Costs additional area, power and must sacrifice stage 2 gain • Can work acceptably well for moderate resistive loads – More later B. Murmann EE315A ― HO #8 12 Gm-C Integrator • Advantages – No OTA, no op amp! OTA op-amp! • Lower power • Less phase shift! – C ti Continuous t i mechanism tuning h i for integrator time constant For H (s ) ≅ Gm sC • Via IBIAS of Gm cell Ro → ∞ B. Murmann • Disadvantages – Nonlinearity of Gm cell – Sensitive to finite output resistance (Ro) – Sensitive to parasitics EE315A ― HO #8 13 Original Paper H. Khorramabadi and P. R. Gray, "High-frequency CMOS continuous-time filters," IEEE J. Solid-State Circuits, vol.19, no.6, pp. 939-948, Dec. 1984. B. Murmann EE315A ― HO #8 14 First-Order Gm-C Filters [Deliyannis, Section 9.2] B. Murmann EE315A ― HO #8 15 Gm-C Biquad B. Murmann EE315A ― HO #8 16 _ + _ C4 C5 _ + + _ _ + _ + + + _ _ + _ + I4 Gm Vout _ L4 + _ + V3 + _ C3 + _ Gm Gm _ Gm _ + L2 + I2 Gm + _ + _ + C2 _ + V1 Gm Gm _ Gm _ + C1 • + _ + _ Gm Gm + + Vin _ Gm _ + _ + _ 5th-Order Gm-C Ladder Filter _ + V5 Can show that capacitor network is unchanged from passive ladder prototype EE315A ― HO #8 B. Murmann 17 Choosing an Implementation Discrete active RC filters Switched-capacitor filters Integrated active RC filters Integrated active Gm-C filters Passive LC filters (discrete) Passive LC filters (integrated) Distributed (waveguide) filters 1kHz B. Murmann 1MHz 10MHz 100MHz EE315A ― HO #8 1GHz 10GHz 18 Active RC versus Gm-C • RC filters (using op-amps) – Superior linearity – Dynamic range ~60-90 dB – Usable signal BW typically up to few tens of MHz • Gm-C – Linearity limited • U Usually h ll have t use d to degeneration, etc. ti t – Dynamic range ~40-70 dB – Distortion performance limited to ~60 dB level – Usable signal BW up to a few hundred MHz • Both implementations typically require some form of tuning B. Murmann EE315A ― HO #8 19 Transconductor Implementation • Hundreds of papers on "linearized" Gm cells p p • Bottom line – Very hard to beat a basic differential pair with (or without) degeneration d ti • Let’s look at a few ideas that have been proposed over the years… B. Murmann EE315A ― HO #8 20 Linearized Gm-Stage Using Triode Device + −≅ io = io − io + Io− Io+ Vin 2 − W ⎛ = μc OX ⎜ L ⎝ R MOSFET 1 1 2 (V GS −VTH )V in − 2V in ⎞ ⎟ ⎠ Vin 2 Second-order nonlinear term is cancelled by a duplicate MOSFET with small VGS control voltage: VC i o = μc OX Vin − VC2 2 − μc OX W ⎛ ⎜ L ⎝ = μc OX W L Io− Io+ + W ⎛ ⎜ L ⎝ Vin 2 1 2 (V GS1−VTH )V in − 2V in ⎞ ⎟ ⎠ 1 2 (V GS 2 −VTH )V in − 2V in ⎞ ⎟ ⎠ ((V GS1−V GS 2)V in ) “ VGS1> VGS2 ” because VC1>VC2 VC1 Z. Czarnul, Y. Tsividis, “MOS tunable transconductor,” Electronics Letters, June 19, 1986, pp. 721-722. EE315A ― HO #8 B. Murmann 21 Composite Gm-Stage to Increase Input Range Gm Wu & Schaumann Io− Io+ + Vin 1 X 4 2 1 X 4 − 1X Vin 2 Vin The net result is increased input range. Linearity is unchanged. Schmook/DeVeirman Io− Io+ + Vin 2 B. Murmann 1X 1 X 4 1 X 4 1X − Vin 2 EE315A ― HO #8 Bipolar implementation by Schmook (1975) and later modified/improved version by DeVeirman (1992). 22 Nauta Cell B. Nauta, “A CMOS Transconductance-C Filter Technique for Very High Frequencies”, IEEE J. Solid-State Circuits, Feb. 1992. B. Murmann EE315A ― HO #8 23 Source-Follower Based Filter S. D’Amico et al., “A 4.1mW 79dB-DR 4th order Source-Follower-Based Continuous-Time Filter for WLAN Receivers”, IEEE J. Solid-State Circuits, Dec. 2006. B. Murmann EE315A ― HO #8 24 Tuning • Various objectives j – Tune out circuit nonidealities such as phase lead/lag – Absorb global process variations • Gm, R C R, – Vary filter bandwidth – Vary other filter parameters • E “b E.g. “boost” i di k d i fil ” in disk drive filters B. Murmann EE315A ― HO #8 25 Q-Tuning V. Gopinathan et al., “Design Considerations for High-Frequency Continuous-Time Filters and Implementation of an Anti-aliasing Filter for Digital Video,” IEEE JSSC, Vol. 25, No. 6, Dec. 1990. B. Murmann EE315A ― HO #7 26 Finite go (Ro) Tuning Dehaene et al., “A 50-MHz Standard CMOS Pulse Equalizer for Hard Disk Read Channels,” IEEE J. Solid-State Circuits, July1997. B. Murmann EE315A ― HO #8 27 Tuning of the Filter Time Constants • • Built using same RC or Gm–C cell used in main filter Lock R (1/Gm) or ( frequency (Gm/C, 1/RC) in a replica to a reference Slave replica's control voltage into main filter circuit Y.P. Tsividis, "Integrated continuous-time filter design - an overview," IEEE Journal of Solid-State Circuits, vol. 29, no. 3, pp.166176, March 1994. B. Murmann EE315A ― HO #8 28 VCO Tuning Example Vin “Vc” controls resistance Vout Main Filter (slave) VC R3 −1 R4 C1 ref Dummy Filter (master) R1 Vc C2 _ oscillator R2 _ + + −1 s R1C1 s R 2C 2 TF ( s ) = 1+ osc. (master) phase C.P. freq detector Vc −1 1 1 1 = + s R 4C1 s R3C1 s R 2C 2 Without R4 s C1C 2 + s C 2G 4 + G 2G3 0 D ( s ) = s C1 C 2 + G 2 G 3 ≡ 0 2 poles at ± j fREF G1G 2 2 G 2 G3 C1C 2 Banu (1985) EE315A ― HO #8 B. Murmann 29 VCF Tuning Approach Use of a low-pass filter, instead of an oscillator, as the reference for tuning Two phases into XOR gate is offset by 90o when phase-locked LP( s ) = ( 2 K ωo ω 2 s 2 + o s + ωo Q fω o Low-pass filter (master) LP( s )| = s = j ωo 1 2 2 ωo + ω2 − ωo + j o XOR C.P. Vc = −90 Q V. Gopinathan et al., “Design Considerations for High-Frequency Continuous-Time Filters and Implementation of an Anti-aliasing Filter for Digital Video,” IEEE JSSC, Vol. 25, No. 6, Dec. 1990. B. Murmann EE315A ― HO #8 30 Discrete Frequency Programming/Tuning Switch in/out capacitors or resistors to control corner frequencies. C3 C2 Possible settings/frequencies: C1, C2, C3, C1+C2, C1+C3, C2+C3, and C1+C2+C3 C1 _ + _ + _ + B. Murmann EE315A ― HO #8 31 Example (1) H. Khorramabadi, “Baseband Filters for 6-95 CDMA Receiver Applications Featuring Digital Automatic Frequency Tuning,” ISSCC 1996. Tuning, B. Murmann EE315A ― HO #8 32 Example (2) H. Khorramabadi, “Baseband Filters for 6-95 CDMA Receiver Applications Featuring Digital Automatic Frequency Tuning,” ISSCC 1996. EE315A ― HO #8 B. Murmann 33 Tuning Gm Over a Wide Range To main circuit G. Bollati et al., “An Eighth-Order CMOS Low-Pass Filter with 30–120 MHz Tuning Range and Programmable Boost,” IEEE J. Solid-State Circuits, July 2001. B. Murmann EE315A ― HO #8 34 Reference Papers (1) • Y. Tsividis, "Integrated continuous-time filter design—an overview," IEEE J. Solid-State Circuits, pp. 15-30, Mar. 1994. • Y. Tsividis, M. Banu, Y Tsividis M Banu and J Khoury “Continuous-Time MOSFET-C Filters in J. Khoury, Continuous-Time VLSI”, IEEE J. Solid State Circuits, Feb. 1986, pp. 15-30; and IEEE Trans. Circuits and Systems, Feb. 1986, pp. 125-140. • Z. Czarnul, “Modification of the Banu-Tsividis Continuous-Time Integrator Structure,” IEEE Transactions on Circuits and Systems, Vol. CAS-33, N 7 pp. St t ” T ti Ci it dS t V l CAS 33 No. 7, 714-716, July 1986. • U.-K. Moon, and B.-S. Song, “Design of a Low-Distortion 22-kHz Fifth Order Bessel Filter,” IEEE Journal of Solid State Circuits, Vol. 28, No. 12, pp. 12541264, Dec.1993. • H. Khorramabadi and P.R. Gray, “High Frequency CMOS continuous-time filters,” IEEE Journal of Solid-State Circuits, pp.939-948, Dec. 1984. • K.S. K S Tan and P.R. Gray, “Fully integrated analog filters using bipolar FET P R Gray technology,” IEEE, J. Solid-State Circuits, pp. 814-821, December 1978. • J. Schmook, “An input stage transconductance reduction technique for high-slew rate operational amplifiers,” IEEE J. Solid-State Circuits, pp. 407-411, Dec. 1975. B. Murmann 35 Reference Papers (2) • A. Durham, J. Hughes, and W. Redman- White, “Circuit Architectures for High Linearity Monolithic Continuous-Time Filtering,” IEEE TCAS, pp. 651-657, Sept. 1992. • C. C Laber and Gray “A 20MHz 6th Order BiCOM Parasitic Insensitive Continuous Gray, A Time Filter and Second Order Equalizer Optimized for Disk Drive Read Channels,” IEEE J. of Solid State Circuits, Vol. 28, pp. 462-470, April 1993. • H. Khorramabadi et al., “Baseband Filters for IS-95 CDMA Receiver Applications Featuring Digital Automatic Frequency Tuning ” ISSCC 1996 pp 172 173 Tuning,” 1996, pp. 172-173. • R. Castello, I. Bietti and F. Svelto, "High-Frequency Analog Filters in Deep-Submicron CMOS Technology", ISSCC Digest of Technical Papers, Feb. 1999, pp.74-75. • Y. Tsividis, Z. Y Tsividis Z Czarnul and S C Fang “MOS transconductors and integrators with S.C. Fang, MOS high linearity,” Electronics Letters, vol. 22, pp. 245-246, Feb. 27, 1986. • I. Mehr and D.R. Welland, “A CMOS Continuous-Time Gm-C Filter for PRML Read Channel Applications at 150 Mb/s and Beyond”, IEEE J. of Solid-State Circuits, Vol.32, No.4, Vol 32 No 4 April 1997 pp 499 513 1997, pp. 499-513. • R. Alini, A. Baschirotto, and R. Castello, “Tunable BiCMOS Continuous-Time Filter for High-Frequency Applications,” IEEE Journal of Solid State Circuits, Vol. 27, No. 12, pp. 1905-1915, Dec. 1992. B. Murmann 36 Reference Papers (3) • J. Khoury, “Design of a 15-MHz CMOS Continuous-Time Filter with On-Chip Tuning”, IEEE J. Solid-State Circuits, Dec. 1991. • B. Nauta, “A CMOS Transconductance C Filter Technique for Very High Frequencies”, A Transconductance-C Frequencies , IEEE J. Solid-State Circuits, Feb. 1992. • G. DeVeirman and R. Yamasaki, “Design of a bipolar 10-MHz continuous-time 0.05deg equiripple linear phase filter,” IEEE J. Solid-State Circuits, pp. 324-331, Mar. 1992. • M. M Banu and Y. Tsividis, “An elliptical continuous time CMOS filter with on chip Y Tsividis continuous-time on-chip automatic tuning,” IEEE J. Solid-State Circuits, pp. 1114-1121, Dec. 1985. • Y. Tsividis and B. Shi, “Cancellation of distortion of any order in integrated active RC filters,” Electron. Lett., pp. 132-134, Feb. 1985. • B. Song, “CMOS RF circuits for data communication applications,” IEEE J. Solid-State Circuits, pp. 310-317, Apr. 1986. • P. Wu and R. Schaumann, “A tunable operational transconductance amplifier with extremely high linearity over a very large input range,” Electron. Lett., pp 1254-1255, y g y y g p g pp. Jul. 1991. • V. Gopinathan, Y. Tsidivis, K-S Tan, R. Hester, “Design Considerations for HighFrequency Continuous-Time Filters and Implementation of an Antialiasing Filter for Digital Video,” IEEE J. Solid State Circuits, pp. 1368-1378, Dec. 1990. g , , pp , B. Murmann 37 Reference Papers (4) • K. Martin and A. Sedra, “Design of signal-flow-graph (SFG) active filters,” IEEE Trans. Circuits Syst., pp. 185-195, 1978. • F. Behbahani, T. Weeguan, A. Karimi-Sanjaani, A. Roithmeier, and A.A. Abidi, “A Karimi Sanjaani, A broadband tunable CMOS channel-select filter for a low-IF wireless receiver,” IEEE J. Solid-State Circuits, pp. 476–489, Apr. 2000. • G. Bollati, S. Marchese, M. Demicheli, and R. Castello, "An eighth-order CMOS lowpass filter with 30-120 MHz tuning range and programmable boost " IEEE Journal of 30 120 boost, Solid-State Circuits, pp.1056-1066, July 2001. • S. Pavan, Y.P. Tsividis, and K. Nagaraj, "Widely programmable high-frequency continuous-time filters in digital CMOS technology," IEEE Journal of Solid-State Circuits, vol.35, no.4, pp.503 511, Circuits vol 35 no 4 pp 503-511 April 2000 2000. • W. Dehaene, M.S.J. Steyaert, and W. Sansen, "A 50-MHz standard CMOS pulse equalizer for hard disk read channels ," IEEE Journal of Solid-State Circuits, vol.32, no.7, pp. 977-988, Jul y1997. • D. Ch l A C th li S Dedieu, and A K i D Chamla, A. Cathelin, S. D di d A. Kaiser, "Di it l T i of Gm-C B "Digital Tuning f C Baseband b d Filters in Configurable Radio Receivers," Proc. ESSCIRC, pp.340-343, Sept. 2006. • S. D’Amico et al., “A 4.1mW 79dB-DR 4th order Source-Follower-Based ContinuousTime Filter for WLAN Receivers”, IEEE J. Solid-State Circuits, Dec. 2006. B. Murmann 38 ...
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This note was uploaded on 08/13/2009 for the course EE 315 taught by Professor Borismurmann during the Spring '09 term at Stanford.

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