A Precise 90&amp;lt;tex&amp;gt;$^circ$&amp;lt;/tex&amp;gt;Quadrature OTA-C Oscillator Tunable in the 50–130-MHz Range

Linares-Barranco, B.; Serrano-Gotarredona, Teresa; Ramos-Martos, J.; Ceballos-Caceres, J.; Mora, J.M.; Linares-Barranco, A.

doi:10.1109/tcsi.2004.823673

Cited by 31 publications

(9 citation statements)

References 18 publications

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“…The circuitry is described in this section, and the electrode and packaging processes are described in §4. Many circuits for sinusoid frequencies have been reported, including a DSP-based solution [25], quadrate oscillators [26,27] and triangle-to-sine generators [28]. The drawback of the DSP-based solution is the large memory requirement for very low frequencies.…”

Section: Impedance Spectroscopy Methodsmentioning

confidence: 99%

High-throughput impedance spectroscopy biosensor array chip

Liu

Mason

2014

Phil. Trans. R. Soc. A.

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Impedance spectroscopy is a powerful tool for characterizing materials that exhibit a frequency dependent behaviour to an applied electric field. This paper introduces a fully integrated multi-channel impedance extraction circuit that can both generate AC stimulus signals over a broad frequency range and also measure and digitize the real and imaginary components of the impedance response. The circuit was fabricated in a 0.5 μm complementary metaloxide semiconductor. Tailored for cellular membrane interface characterization, the signal generator produces sinusoidal waves from 10 mHz to 10 kHz. To suit a variety of applications, the impedance extraction circuit provides a programmable current measurement range from 100 pA to 100 nA with a measured resolution of approximately 100 fA. Occupying only 0.045 mm 2 per measurement channel, the circuit is compact enough to include nearly 200 channels in a 3 × 3 mm 2 die area.

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Section: Impedance Spectroscopy Methodsmentioning

confidence: 99%

High-throughput impedance spectroscopy biosensor array chip

Liu

Mason

2014

Phil. Trans. R. Soc. A.

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“…If we define a characteristic voltage as subthreshold above threshold (3) and the transconductance gain as , then we can write (1) and (2) as (4) where is a sigmoidal function that depends on the region of operation. In general, it would also depend on the specific OTA topology.…”

Section: A Output Currentmentioning

confidence: 99%

“…The nonlinearity may be external to the SOS [1]- [4] or may be an inherent part of it [5], [6]. We espouse the latter approach and present in this paper a general method for synthesizing a sinusoidal oscillator this way.…”

Section: Ota-c Oscillator Synthesismentioning

confidence: 99%

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Theory and Design of OTA-C Oscillators with Native Amplitude Limiting

Odame

Hasler

2009

IEEE Trans. Circuits Syst. I

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An analog sinusoidal oscillator usually involves some form of amplitude-limiting mechanism. We examine operationaltransconductance-amplifier (OTA) nonlinearity as a choice for amplitude limiting and develop a general theory for its use in OTA-capacitor (OTA-C) oscillators. We facilitate our theoretical discussion with an illustrative design example that we fabricated and tested.Index Terms-Nonlinear oscillators. I. OSCILLATOR DESIGN APPROACHEST HE SINUSOIDAL oscillator is a basic analog-circuit component in communication and instrumentation systems. High-quality oscillators usually involve inductor-capacitor networks and are used in RF systems. However, the inductance values required for low-and moderate-frequency oscillators cannot practically be realized in integrated circuits. Ring oscillators provide much better economy in terms of size, but they are limited to such uses as clock generation due to their high harmonic content. Operational transconductance amplifier-capacitor (OTA-C) oscillators, on the other hand, operate at low to moderate frequencies with fairly high spectral purity and are compact enough for integration. An OTA-C oscillator is typically designed as an unstable second-order system that is regulated by some nonlinear amplitude-limiting circuitry. Buonomo et al. [1] identified a set of conditions on the nonlinearity for the system to exhibit oscillation. The most common implementations of an amplitude limiter are a piecewise-linear resistor and an automatic gain control circuit [1]- [4]. A third possibility is to use the inherent nonlinear behavior of an OTA as an amplitude limiter.The success of using OTA nonlinearity, as reported in the literature, has been mixed. This approach is considered in [3], but the results are only poorly controlled distorted oscillations. The approach is also mentioned in [2] but is characterized as yielding only unpredictable oscillations. On the other hand, the results in [5], [6], and [7] show success in designing sinusoidal oscillators based on OTA nonlinearity. However, none of these papers, nor, to our knowledge, any other sources in the literature, provide a systematic and analytical presentation of how exactly to exploit OTA nonlinearity in a general second-order oscillator structure. This is a relevant lack, as an oscillator that Manuscript Fig. 1. OTA converts a differential voltage input into an output current. A differential pair of transistors is at the heart of the voltage-current conversion. An attenuating stage may exist between the voltage input and the differential pair. A current-subtraction network combines the drain currents of the differential-pair transistors into a single output.properly exploits OTA nonlinearity can easily confer power and area savings, since no external amplitude-limiting scheme is required. For instance, a slight redesign of the oscillator in [2] could have used one of the existing OTAs as an amplitude limiter, precluding the need for the extra piecewise-linear (PWL) circuit that its authors describe.This paper provides ...

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“…Quadrature oscillators have also been reported for generating quadrature signals [7], [8]. In an oscillator-based sinusoid signal generator, the frequency is controlled by a tunable component in the circuit, such as a resistor, a capacitor, or a transconductor.…”

Section: Introductionmentioning

confidence: 99%

Fully Integrated Seven-Order Frequency-Range Quadrature Sinusoid Signal Generator

Yang

Mason

2009

IEEE Trans. Instrum. Meas.

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Abstract-A compact wide-frequency-range quadrature sinusoid signal generator tailored to on-chip impedance spectroscopy instrumentation applications is described. Using a new hybrid structure, it provides seven orders of frequency-tuning range (1 mHz to 10 kHz) appropriate for impedance characterization of many sensor materials. The signal generator exhibits very accurate frequency tuning through digital control, and the new structure inherently guarantees good phase and amplitude matching between sine and cosine outputs across the supported frequency range. The circuit has been fabricated in a 0.5-μm CMOS process and occupies 1 mm 2 . It consumes only 60 μA with a 3-V supply. Measurements show that the phase mismatch is less than 0.8• and that the amplitude mismatch is less than 3%. The total harmonic distortion is below 0.6% over the seven-order frequency range.Index Terms-Analog filter, impedance measurement, quadrature signal generator, sinusoid signal generators, wide-frequencyrange frequency tuning.

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A Precise 90<tex>$^circ$</tex>Quadrature OTA-C Oscillator Tunable in the 50–130-MHz Range

Cited by 31 publications

References 18 publications

High-throughput impedance spectroscopy biosensor array chip

High-throughput impedance spectroscopy biosensor array chip

Theory and Design of OTA-C Oscillators with Native Amplitude Limiting

Fully Integrated Seven-Order Frequency-Range Quadrature Sinusoid Signal Generator

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