IEEE SENSORS JOURNAL, VOL. 9, NO. 2, FEBRUARY 2009 135

A Fully Differential PotentiostatSteven M. Martin, Member, IEEE, Fadi H. Gebara, Timothy D. Strong, Member, IEEE, and

Richard B. Brown, Senior Member, IEEE

AbstractLow-voltage, single-ended (SE) potentiostats are un-able to detect many analytes of interest because the oxidation po-tentials of these analytes are greater than the voltage that the po-tentiostat can deliver to the electrodes. In this work, a fully-dif-ferential (FD) potentiostat is described which enables detection ofa wide range of analytes using a supply voltage of 1.8 V. The FDpotentiostat was implemented in TSMCs 0.18 m CMOS processand has been verified experimentally. A theoretical discussion ofthe FD potentiostat is given and comparisons to SE potentiostatsare provided. Biological and environmental analytes are chemi-cally detected using the FD potentiostat.

Index TermsChemical transducers, CMOS analog integratedcircuits, electrochemical analysis, potentiostat.

I. INTRODUCTION

T RANSDUCERS which utilize electrochemical sensingprinciples are capable of detecting many important ana-lytes and are utilized in applications such as biomedical devices,environmental monitoring, and laboratory research [1], [2].A common electrochemical transducer for the study of liquidanalytes is the amperometric sensor. The electronic interfacefor these transducers is a circuit known as a potentiostat [3].The potentiostat serves two main functions. It is used to inducea specified potential drop between a sensing electrode and aliquid solution. It also serves to amplify the resulting currentfrom the chemical reaction at the sensing electrode. Histor-ically, the induced voltage was held constant throughout anexperiment. However, many current electrochemical analyses,known as voltammetric techniques, continuously vary theapplied potential.

Research on integrated CMOS potentiostats generally fallsinto three categoriespotentiostats designed to improve accu-racy and detection limit, multiple potentiostats integrated ontoa single chip for biological array applications, and potentiostats

Manuscript received May 13, 2008; accepted June 21, 2008. Current versionpublished January 09, 2009. This work was supported in part by a U.S. NationalScience Foundation Graduate Research Fellowship and by the Engineering Re-search Centers Program of the U.S. National Science Foundation under AwardEEC-9986866. The associate editor coordinating the review of this paper andapproving it for publication was Prof. Evgeny Katz.

S. M. Martin was with the University of Michigan, Ann Arbor, MI 48109USA. He is now with Avago Technologies, Fort Collins, CO 80525 USA(e-mail: stevenmm@umich.edu).

F. H. Gebara was with the University of Michigan, Ann Arbor, MI 48109USA. He is now with IBM Research, Austin, TX 78753 USA (e-mail: fhgebara@us.ibm.com).

T. D. Strong was with the University of Michigan, Ann Arbor, MI 48109USA. He is now with GE Analytical Instruments, Ann Arbor, MI 48108 USA(e-mail: strongtd@ieee.org).

R. B. Brown was with the University of Michigan, Ann Arbor, MI 48109USA. He is now with the University of Utah, Salt Lake City, UT 84112 USA(e-mail: brown@utah.edu).

Digital Object Identifier 10.1109/JSEN.2008.2011085

integrated with mixed-signal functionality. Wei et al. [4]demonstrated a chopper-stabilized potentiostat to improve DCoffset, Kakerow et al. [5] demonstrated a switched-capacitorpotentiostat for high accuracy measurements, Breten et al. [6]demonstrated an integrating potentiostat with dual-slope ADCfor improved detection limits, and Martin et al. [7] demon-strated a pseudo-differential potentiostat to enable a highlyaccurate analysis technique known as subtractive anodic strip-ping voltammetry. Bandyopadhyay et al. [8] implemented adistributed potentiostat system for neural applications. Schienleet al. [9], created arrays of potentiostats for DNA applications.Others have demonstrated potentiostats integrated with dataconverters [10], [11], with digital control [12], on general pur-pose microcontrollers [13], and with the amperometric sensorsthemselves [9], [12], [14], [15].

These potentiostat designs, however, do not address the prob-lems that arise when the supply voltage is scaled. An analytecan be detected only when the applied potential is in excess ofthe chemical species standard potential. (This is described ingreater detail in Section II.) As the supply voltage is scaled, thenumber of detectable analytes is reduced because the maximumpotential difference that can be applied between the electrodeand the solution is diminished. Narula et al. [16] demonstrateda potentiostat that improved the dynamic range of chemical sen-sors in low-voltage processes by dynamically translating thesensor signals into time-encoded values. That potentiostat, how-ever, did not address the reduction in maximum applied elec-trode potential. Furthermore, its dynamic range can degrade asthe rate of the voltammetric sweep increases.

All aforementioned potentiostats utilized a single-ended(SE) architecture. This work, which extends a short conferencepaper [17], describes a fully differential (FD) potentiostat thatdoubles the dynamic range of the system, but more importantly,maximizes the number of detectable analytes for a given supplyvoltage. The FD potentiostat was implemented in TSMCs0.18 CMOS process and operates with a nominal supplyvoltage of 1.8 V. This process and operating voltage werechosen because the potentiostat was designed as a standardcell for the low-power, mixed-signal, WIMS microcontroller[18]. The WIMS microcontroller can serve as a platform formany integrated sensing applications which require chemicaldetection including remote environmental monitoring andneural prosthesis.

An introduction to electrochemical sensors is presentedin Section II. In Section III, a standard, SE potentiostat isdescribed. The FD potentiostat is presented in Section IV andcompared to the SE potentiostat. Measured characteristicsfor both circuits are given. Electroanalytical experiments per-formed using the FD potentiostat are also reported.

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136 IEEE SENSORS JOURNAL, VOL. 9, NO. 2, FEBRUARY 2009

II. ELECTROCHEMISTRY REVIEW

The following description highlights only the aspects of elec-troanalytical chemistry which are germane to understanding thedevelopment of the FD potentiostat. The interested reader is di-rected to Bard et al. [3] for a more detailed discussion of elec-trochemistry.

A. Faradaic Current

Under equilibrium, and in the absence of an externally ap-plied voltage, a single polarizable electrode resting in solutionwill develop a potential based on the ratio of the solutionschemical species [3]. When a voltage sufficiently larger than thisequilibrium potential (an overpotential) is applied to the elec-trode, this forces the system out of equilibrium and results in areduction/oxidation (redox) reaction of the form

(1)

where is the oxidized form of the species, is the number ofelectrons per molecule oxidized or reduced, is an electron,and is the reduced form of the species. For every reductionor oxidation, electrons are transferred from solution to elec-trode or vice versa. This results in a faradaic current at theelectrode surface. Among other parameters, is a function ofthe concentration of the oxidized species and the electrode area.Thus, the measured faradaic current corresponds to a specificion concentration.

B. Overpotentials

In aqueous solutions, the overpotential required to induce aredox reaction for a given chemical species is approximatelyequivalent to that species standard potential [3]. If a sufficientoverpotential cannot be applied to the electrode, then an an-alytical measurement of that chemical species cannot be ob-tained. Using a platinum electrode, a water-based solution tendsto breakdown for overpotentials more positive than 1.5 V andmore negative than [19]. Applying overpotentials out-side of is of minimal analytical value. As we will see inSection III, a standard, SE potentiostat operating with a voltagesupply below 3 V, cannot detect every species within waterspotential window. This is an important (and detrimental) con-sequence of operating in low-voltage processes and led to thedevelopment of the FD potentiostat.

C. Amperometric Sensors

Single electrode systems are operationally impractical. A typ-ical sensor configuration is the three-electrode amperometriccell. The three electrodes are: the auxiliary electrode (AE), thereference electrode (RE), and the working electrode (WE), asshown in Fig. 1(a). The faradaic reaction of interest occurs at theWE. The RE, which ideally draws zero current, is a nonpolariz-able electrode that tracks the solution potential. Consequently,the potential between the electrode and solution which inducesthe faradaic reaction, is given by

(2)

Fig. 1. Three-electrode amperometric sensor. (a) Schematic representation.(b) Simplified electrical-equivalent model.

where and are the potentials at the WE and RE, re-spectively. The amperometric cells potential is defined by(2). The AE enables the potential of the solution to be set viasecondary redox reactions and sources the current necessary forthe faradaic reaction.

Fig. 1(b) shows an electrical-equivalent model of a three-elec-trode amperometric cell. Solution impedances, which are typi-cally small, are neglected. and represent faradaic resis-tances, and and are the double-layer capacitances as-sociated with the AE and WE, respectively. These double-layercapacitances are given by

(3)

where is the capacitance of electrode , is the area of theelectrode , and is a constant with an approximate value of0.36 [20]. is defined as

(4)

Note, that if changes, must be recalculated based onthe measured . It is inappropriate to assume that an increasein necessarily causes an increase in . Recall that isproportional to electrode area. Since, the AE is designed to bemuch larger than the WE, .

A microfabricated, platinum (Pt) WE measuring 0.004was used in this work [21]. The double-layer capacitance of thisWE was approximately 1.4 nF, and for chemical concentrationsin the millimolar range, was approximately 1 . The AEwas a platinum wire with a measured double-layer capacitanceof approximately 1 uF and an of approximately 10 . Amacrosized saturated calomel RE was used.

For low frequencies, the electrical-equivalent sensor modelsimplifies into two series resistors. This two-resistor model,with and , is used for the remainderof the analyses in this work.

MARTIN et al.: A FULLY DIFFERENTIAL POTENTIOSTAT 137

Fig. 2. SE potentiostat.

III. SINGLE-ENDED (SE) POTENTIOSTATFig. 2 shows a typical potentiostat using the standard, SE

topology [3]. As stated previously, a primary function of the po-tentiostat is to ensure that tracks an applied source voltage,

, under varying current-loading conditions. The negativefeedback around opamp creates a virtual ground at the WE.Thus, neglecting opamp offset, is given by

(5)

The REs potential is buffered by to ensure that no cur-rent is drawn through the RE. The negative feedback around

(which is connected via the amperometric cell) forces nodeto ground. The voltage seen at node is 1/2 of the sum of

and . It follows that node is only equal to zero (ground)when or by (5), when . Thus, the neg-ative feedback of the potentiostat ensures that tracks .

Since the WE is statically held at virtual ground, the value ofcan only be altered by changing the potential at the AE.

This limits the use of the SE potentiostat in low-voltage sys-tems-on-chip (SoC). The voltage swing of in the SE archi-tecture, , assuming that has rail-to-rail output, is thendefined by the voltage swing at the AE

(6)

where is the positive supply voltage and is the negativesupply voltage.

The potentiostat also amplifies the sensors faradaic current.This is accomplished with . The sensors current flowsthrough (which is referenced to virtual ground) to providean amplified current-to-voltage conversion such that

(7)

IV. FULLY DIFFERENTIAL POTENTIOSTAT

A. TheoryThe new, fully differential potentiostat is shown in Fig. 3. In

contrast to the SE architecture, the FD potentiostat can dynam-ically control the voltages on both the auxiliary and WEs. TheFD potentiostat can, thus, double the voltage range of the SE

Fig. 3. Fully differential potentiostat.

version. The circuit operates as follows. The potentials on boththe reference and WEs are buffered by and and aresummed with the differentially applied source voltage. Since theFD opamp, , is configured for negative feedback, the differ-ential voltage at its input terminals is ideally equal to zero andis given by

(8)

Rearranging this equation yields

(9)

The right-hand side of this equation is equivalent to the cellvoltage and thus, the FD potentiostat works to ensure thattracks .

Assuming that has rail-to-rail output, the voltage swingfor the FD potentiostat , is given by

(10)

Comparing this to the swing of the SE potentiostat yields

(11)

Assuming is negligible, the voltage swing is doubled.serves to develop a voltage proportional to the faradaic currentand is inserted in each half of the circuit to maintain symmetryaround ground. The voltage across is differentially bufferedusing and , and the output of the FD potentiostat isgiven by

(12)

Equations (10) and (12) demonstrate a tradeoff in sizing .Increasing the value of , increases the gain of the circuit, but italso reduces the signal swing of the FD potentiostat. In practice,this is not a concern since typical currents from microelectrodesare in the microampere range or below. Thus, if is 10 thevoltage drop across is only 10 mV.

In addition to the improved signal swing, the FD potentiostatsuppresses common-mode noise and doubles the dynamic rangeof the sensors output due to its differential nature [22].

138 IEEE SENSORS JOURNAL, VOL. 9, NO. 2, FEBRUARY 2009

Fig. 4. Magnitude of versus opamp gain and .

B. Nonidealities

Since the FD potentiostat is composed of opamps, it is in-structive to examine how opamp nonidealities affect the func-tion of the circuit. These are compared to nonidealities in theSE potentiostat. The analyses presented in this section utilizethe low-frequency, electrical-equivalent sensor model.

1) Open-Loop Gain: Let be the open-loop gain of opamp. Assuming that , a detailed circuit analysis of the

FD potentiostat yields

(13)Fig. 4 shows the plot of (13) versus the choice of , the open-loop gain , and the open-loop gain . For , a gain ofabout 100 (40 dB) sets the transfer function close to the idealvalue of 1. To make the transfer function tolerant of large valuesof , and thus achieve higher gains, opamp requires anopen-loop gain of nearly 10 000 (80 dB). The transfer functionfor the SE potentiostat has a similar form given by

(14)

The requirements of are similar to those of in theFD potentiostat.

2) Opamp Offset: The circuit analysis of the FD potentiostatincluding opamp offset yields a cell voltage offset given by

(15)

where is the offset of . Comparatively, the equation forthe offset in the SE potentiostat is approximated by

(16)

if is assumed to be much greater than 2. Note the similaritybetween (15) and (16). Thus, the cell potentials offset is similarfor the FD and SE potentiostats.

The amplification of the faradaic current to an output voltagealso suffers from offset problems. Unfortunately, the FD poten-tiostats output voltage has double the offset variation of the SEversions output voltage.

3) Noise: Electronic noise on the cell potential is of negli-gible concern due to its small value compared to typical appliedvoltages and the fact that the typical impedance between thesolution and the WE is large. Noise on the signal output volt-ages, however, directly affects the minimum detectable signal(or chemical concentration) of the circuit. In the absence ofleakage currents, the only current that can flow through isthe faradaic current and the equivalent input-noise current of

as it flows to the output of . The signal-to-noise ratio(SNR) of the FD potentiostat is given by

(17)

where is the equivalent squared input current noise of ,is the equivalent squared input voltage noise of , andis the equivalent squared noise of . The SE potentiostats

SNR is given by

(18)

where is the equivalent squared input current noise ofand is the equivalent squared noise of . The FD poten-tiostat has an additional voltage noise term in the denominatorwhich lowers its SNR. Thus, to achieve performance equiva-lent to the SE potentiostat, the FD circuit must reduce the noiseassociated with and . This can require larger bias cur-rents and/or larger device geometries depending on the domi-nant form of the opamp noise. In ultra-low-current applications,

and can be sized in the multimegaohm range and re-sistor thermal noise may overpower the noise from the activeelectronics.

C. DesignBoth FD and SE potentiostats were implemented in TSMCs

0.18 CMOS process using the nominal supplyvoltage. As shown in (13) and (14), large gains are requiredfor and . The common-mode range of the signalscan occur anywhere within the range of the supplies, thereforeopamps with rail-to-rail inputs are required. To achieve the max-imum signal swing, the opamps must also have rail-to-rail out-puts. Additionally, the outputs must drive the large double-layercapacitances of the working and AEs. Based on these require-ments, the opamps were designed using an architecture pre-sented in [23] that combines a rail-to-rail input stage, folded-cascode gain stage, and class AB common-source output stage.The schematic of the FD opamp is shown in Fig. 5. The tran-sistor dimensions are given in micrometers. The SE opampshave a similar topology, but do not require the common-modefeedback (CMFB) circuit, have a diode connection in each halfof the folded-cascode stage, and have only a single branch ofthe class AB output stage. The compensation capacitors wereset to 5 pF to ensure stability. For the specified values of the

MARTIN et al.: A FULLY DIFFERENTIAL POTENTIOSTAT 139

Fig. 5. Fully differential opamp.

Fig. 6. Micrograph of the potentiostat test chip.

three-electrode cell and this value of compensation capacitor,the simulated phase margin of the FD opamp was 51 .

Resistors and were chosen to provide identical cur-rent-to-voltage gains while still maintaining adequate signalswing. Both and were set to 10 and implemented ina high-resistance polysilicon layer. Resistors and werealso set to 10 .

V. EXPERIMENTAL RESULTSFig. 6 is a micrograph of the 0.18 potentiostat test chip.

All bond pads were connected to standard ESD structures. TheESD transistors measured 2800 /0.36 . The FD and SEopamps were experimentally verified. Both opamps had open-loop gains greater than 90 dB, bandwidths equal to approxi-mately 440 kHz into a 16 pF load, and full-scale output volt-ages at 4 kHz into 0.1 uF loads, slew rates greater than 0.5 V/us,PSSR values greater than 80 dB, and input resistances greater

Fig. 7. (a) . (b) Sinusoidal control of both RE and WE.

than 100 . The FD opamp consumed 533 , whereas theSE opamp consumed 225 .

A dummy load cell with and set to 10 and 1 ,respectively, was used to characterize the potentiostats. Fig. 7(a)is a plot of the transfer function from to for both theFD and SE potentiostats. The plot shows that the transfer func-tion is close to unity for both cases. As predicted by theory, theswing of the FD potentiostat is twice the swing of the SE poten-tiostat. An oscilloscope screen capture [Fig. 7(b)] shows that inthe FD potentiostat both the RE and WE voltages are dynam-ically changing. Note, that although the signal is almost twicethe supply voltage, no clipping of occurs. The offset of

was measured on 22 different dice. The mean offset forthe FD potentiostat was , whereas the mean offsetfor the SE potentiostat was 0.7 mV. The standard deviations

140 IEEE SENSORS JOURNAL, VOL. 9, NO. 2, FEBRUARY 2009

Fig. 8. versus temperature.

Fig. 9. On-chip gain for the (a) FD potentiostat and (b) SE potentiostat.

of the offsets for the FD and SE potentiostats were 2.7 and3.1 mV, respectively. The drift of over 24 h was measuredas and for the FD and SE potentiostats,respectively. The transfer function to was also mea-sured versus temperature. This is an important specification ifthe potentiostat is integrated onto a substrate with circuits dissi-pating large amounts of power. Fig. 8 shows the plot of transferfunction magnitude and offset versus operating temperature. Fitto straight lines, the temperature coefficients for slope error are20 and 50 for the FD and SE potentiostats, re-spectively. The offset scales similarly for both potentiostats at

.

To further amplify the output voltage before sending thesignal off chip, the of both the FD and SE potentiostatswas routed through on-chip gain stages as shown in Fig. 9. Theoutput noise was measured using a high-impedance active probe(Agilent 48100A) connected to a spectrum analyzer. Fig. 10shows the noise spectral density for the FD potentiostatsoutput. The total integrated noise in a 500 Hz bandwidth for the

Fig. 10. Noise spectral density of FD potentiostats output.

TABLE ISUMMARY OF CHARACTERIZATION RESULTS

FOR THE FD AND SE POTENTIOSTATS

FD and SE potentiostats was 2.5 and 2.9 mV, respectively. Mostchemical experiments are not operated above 500 Hz. Due tothe FD potentiostats differential nature, the dynamic range of

is expected to improve by 6 dB. Since the measured outputnoise of the FD potentiostat was slightly lower than the noisein the SE potentiostat, the dynamic range improved by 7 dB.

The FD potentiostat increased the common-mode signal re-jection by over 20 dB versus the SE potentiostat. This noise re-jection was ultimately limited by on-chip resistor matching. Thegain error versus temperature was for both poten-tiostats while the FD potentiostat had a gain offset variation of

and the SE potentiostat had a gain offset variationof . These results indicate that the FD potentiostatis well-suited for integrated system-on-chip (SoC) applications,where low voltages and high switching noise are common.

Table I compares the two potentiostats based on measureddata. The supply currents were large because the opamps weredesigned for 1 nF loads to facilitate use of the potentiostats withmacroelectrodes if necessary. Additionally, to speed develop-ment, only high-current opamps were implemented. With fur-ther optimization and exclusive use of the potentiostats with mi-croelectrodes, the power consumption could be reduced to themicrowatt range and could provide for long-term, remote SoCuse.

VI. ELECTROCHEMICAL ANALYSESThe FD potentiostat and the previously described microfabri-

cated amperometric sensor were used to perform electrochem-ical analyses. Fig. 11 shows cyclic voltammograms (CVs) [3]for the detection of using a Pt electrode in a solution of 5mM NaBr, 100 mM NaCl electrolyte. Bromide has a standard

MARTIN et al.: A FULLY DIFFERENTIAL POTENTIOSTAT 141

Fig. 11. CV of NaBr using a commercial potentiostat (ideal), and the FD andSE integrated potentiostats.

Fig. 12. Chemical calibration curves for (a) and (b) dopamine .

potential which is outside the range of the SE potentiostat. Thedata was captured using both the FD and SE potentiostats andalso using a nonvoltage-limited commercial potentiostat whichgenerated the curve labeled ideal. The parameters of the CVare as follows: starting potential of 500 mV, final potential of1.2 V, scan rate of 1 V/s, and a step size of 2 mV. The figureclearly shows that the redox potential of renders the SEpotentiostat incapable of accurately capturing either the anodicor cathodic peaks of the CV, whereas the CV captured with theFD potentiostat closely resembles the ideal curve. A calibra-tion curve was obtained for by varying the concentrationof NaBr dissolved into the solution. The results are shown inFig. 12. The plot is in agreement with electrochemical theory(i.e., it is linear) with an value of 0.98.

The FD potentiostat was next used to determine calibrationcurves for the neurotransmitter dopamine and the toxic metallead (Pb). Dopamine was dissolved in 10 mM phosphate buffersolution, pH 7.4, in concentrations of 0.2 to 10 mM and lead

solutions were created with concentrations from 0.6 to 1 in100 mM KCl, pH 4.3 buffer solution. Dopamine was detectedusing CVs with the following parameters: starting potential of1.2 V, final potential of , scan rate of 2 V/s, and astep size of 2 mV. Lead was detected using CVs with the fol-lowing parameters: starting potential of 300 mV, final poten-tial of , scan rate of 1 V/s, and a step size of 2 mV.The resulting calibration curves (Fig. 12) are plots of the peakoutput voltage versus concentration. The calibration curves arelinear with values of 0.97 and 0.94 for dopamine and Pb,respectively.

VII. CONCLUSIONA new circuit, the FD potentiostat, has been developed that

enables chemical microtransducers to detect a large suite of ana-lytes even when implemented in modern, low-voltage processes.The FD potentiostat was fabricated in TSMCs 0.18 CMOSprocess and experimentally verified. Electrochemical analyseswere conducted using the potentiostatic test chip and a micro-fabricated amperometric sensor. Results from these experimentsshow good agreement with electrochemical theory. The FD po-tentiostat will enable a large number of analytes to be senseddespite their oxidation and reduction potentials being outsidethe voltage range of modern semiconductor processes.

ACKNOWLEDGMENTThe authors would like to thank the MOSIS MEP research

support program for fabrication of the potentiostat test chip.

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Steven M. Martin (S99M05) received the B.S.degree from the University of Florida, Gainesville,in 1999, and the M.S. and Ph.D. degrees in electricalengineering from the University of Michigan, AnnArbor, in 2001 and 2005, respectively.

He has designed high-speed I/O links for theItanium line of processors from Intel, and has alsoworked with several startups where he developedsensor interface and system electronics for next gen-eration biomedical devices. He currently serves asan Adjunct Professor at Colorado State University.

He currently develops orthogonal sensor technologies and products for AvagoTechnologies. He coauthored a book chapter on chemical sensor interfaces. Hecontinues to conduct research in the area of transducers and high-performancecircuits.

Dr. Martin serves as an Officer of the Denver Solid-State Circuit Society. Hewas the recipient of an NSF Graduate Research Fellowship in 2000 and in 2008,

Fadi H. Gebara was born in Detroit, MI, in 1978. Hereceived the B.S., M.S., and Ph.D. degrees in elec-trical engineering from the University of Michigan,Ann Arbor, in 2000, 2002, and 2005, respectively.

In 2004, he began work at the IBM Austin Re-search Laboratory and in 2005, he became a researchstaff member. During his time at IBM, he has devel-oped numerous clocking strategies for high-perfor-mance microprocessors. Currently, he is working onadaptive cache designs for reduced latency and in-creased throughput.

Timothy D. Strong (S91M92) received the B.S.degree from Michigan Technological University,Houghton, in 1992, the M.S. degree and the Ph.D.degree in electrical engineering from the Univer-sity of Michigan, Ann Arbor, in 1997 and 2004,respectively.

He worked from 1992 to 1995, as a Design En-gineer for International Business Machines Corpora-tion, Burlington, VT, developing high-end micropro-cessors. From 2004 to early 2008, he conducted re-search and development of drinking water test equip-

ment for Sensicore, Inc., Ann Arbor. He is currently with General Electric An-alytical Instruments and is involved in research on portable amperometric andpotentiometric water quality test instruments.

Richard B. Brown (S74M76SM91) receivedthe B.S. and M.S. degrees in electrical engineeringfrom Brigham Young University, Provo, UT, in1976 and the Ph.D. degree in electrical engineering(solid-state sensors) from the University of Utah,Salt Lake City, in 1985.

From 1976 to 1981, he was Vice-President of Engi-neering at Holman Industries, Oakdale, CA, and thenManager of Computer Development at Cardinal In-dustries, Webb City, MO. In 1985, he joined the fac-ulty of the Department of Electrical Engineering and

Computer Science, University of Michigan, Ann Arbor. He became Dean ofEngineering at the University of Utah in July 2004. He has conducted major re-search projects in the areas of solid-state sensors, mixed-signal circuits, GaAsand silicon-on-insulator circuits, and high-performance and low-power micro-processors.

Prof. Brown is a member of ACM. He is Chairman of the MOSIS AdvisoryCouncil for Education. He was Chair of the 1997 Conference on Advanced Re-search in VLSI and the 2001 Microelectronic System Education Conference. Hehas served as Guest Editor of the IEEE JOURNAL OF SOLID-STATE CIRCUITS andPROCEEDINGS OF THE IEEE, and as Associate Editor of IEEE TRANSACTIONSON VERY LARGE SCALE INTEGRATION (VLSI) SYSTEMS.