• 제어로봇시스템학회:학술대회논문집
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• 1999.10a
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• pp.259-261
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• 1999

An operational transconductance amplifier (OTA) based precision full-wave rectifier circuit is presented in this article. The proposed circuit has a very sharp corner in the DC transfer characteristic and simple configuration comprised three OTAs and one current mirror. The temperature dependence of the OTA transconductance is reduced. Experimental results demonstrating the characteristic of the circuit are included.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.229-232
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• 2005

This paper presents the OTA-based current differencing buffered amplifier (CDBA), which has a simple configuration comprised four OTAs. The proposed circuit is ease of design and suitable for analog signal processing applications in both voltage and current modes. The first order allpass filters were implemented as the application examples in order to demonstrate the performances of the proposed CDBA. PSPICE analog simulation and the commercially available OTAs-based experimental results verifying the circuit performances are also included.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.10
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• pp.8-16
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• 1999

This paper presents a new simulation-based analog cell synthesis approach with improved simulation efficiency For the hierarchical synthesis of analog cells we developed the sub-circuit optimizers such as current mirror and differential input stage. Each sub-circuit optimizer can be used for synthesis of analog cells such as OTA(operational transconductance amplifier), 2-stage OP-AMP and comparator. To reduce the time spending of the simulation-based synthesis we propose 2-stage searching scheme and simulation data reusing scheme. With those schemes the synthesis time spending of OTA was reduced from 301.05sec to 56.52sec by 81.12%. Since our synthesis system doesn't need other additional physical parameters except SPICE parameters, and is independent of the process and its model level, the time spending to port to other process is minimized. We synthesized OTA and 2-stage OP-AMP respectively with our approach to show its usefulness.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.11
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• pp.83-91
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• 1990

VOC(coltage controlled oscillator) circuits are necessary in applications such at the demodul-ation of FM signals, frequency synthesizer, and for clock recovery from digital data. In this paper, we designed the VCO circuit based on a OTA(operational transconductance amplifier) and the OP amp which using a differential amplifier by BiCMOS circuit. It consists of a OTA, voltage contorolled integrator and a schmitt trigger. Conventional VCO circuits are designed using the CMOS circuit, but in this paper we designed newly BiCMOS VCO circuit which has a good drive avlity, As a result of SPICE simulation, output frequency is 141KHz at 105KHz, and sensitivity is 15KHz.

• ETRI Journal
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• v.35 no.2
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• pp.226-233
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• 2013

This paper presents a two-stage power-efficient class-AB operational transconductance amplifier (OTA) based on an adaptive biasing circuit suited to low-power dissipation and low-voltage operation. The OTA shows significant improvements in driving capability and power dissipation owing to the novel adaptive biasing circuit. The OTA dissipates only $0.4{\mu}W$ from a supply voltage of ${\pm}0.6V$ and exhibits excellent high driving, which results in a slew rate improvement of more than 250 times that of the conventional class-AB amplifier. The design is fabricated using $0.18-{\mu}m$ CMOS technology.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.7
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• pp.80-85
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• 1996

A sinusoidal tuned VCO based on linear OTA's has been designed for instrumentation and measurement applications. It consists of a noniverting amplifier, a hard limiter, and a current controlable LC-tuned circuit which is realized vy two linear OTA's and two grounded capacitors. A prototype circuit has been built with discrete components. The experimental results show that the proposed VCO has a linearity error of less than 6.5 percent and a temperature coefficient of less than 200ppm/$^{\circ}C$ over a bias current range form 5$\mu$A to 100 $\mu$A(or an oscillation frequency range form 775.5 Hz to 20.371 kHz). A total harmonic distortion of 0.6 percent was measured for a peak-to-peak amplitude of 5V.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.8
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• pp.1260-1264
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• 1990

A voltage controlled CMOS operational transconductance amplifier (OTA), whose transconductance is directly proportional to the DC bias voltage, has been designed for many electronic circuit applications. It consists of a differential pair and three ourrent mirrors. The SPICE simulation shows that the conversion sensitivity of the OTA is 41.817 \ulcornerho/V and the linearity error is less than 0.402% over a bias voltage range from -2. OV to 1. OV. Electrically tunalble filters based on voltage controlled impedances, which are realized with OTA's, also have been designed. The SPICE simulation shows that a second-order bandpass filter, whose center frequency is 23KHz at -1. OV, has the conversion sensitivity 6.6KHz/V and the linearity error less than 0.822% over a voltage range from -2.OV tp 1.OV, Tne OTA has been laid out with the 3\ulcorner n-well CMOS design rule adopted in ISRC (inter-university semiconductor research center). The chip size was about $0.756x0.945mm^2$.

• ETRI Journal
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• v.42 no.4
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• pp.534-548
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• 2020

This study presents a new architecture for a field programmable analog array (FPAA) for use in low-frequency applications, and a generalized circuit realization method for the implementation of nth-order elliptic filters. The proposed designs of both the FPAA and elliptic filters are based on the operational transconductance amplifier (OTA) used in implementing OTA-C filters for biopotential signal processing. The proposed FPAA architecture has a flexible, expandable structure with direct connections between configurable analog blocks (CABs) that eliminates the use of switches. The generalized elliptic filter circuit realization provides a simplified, direct synthetic method for an OTA-C symmetric balanced structure for even/odd-nth-order low-pass filters (LPFs) and notch filters with minimum number of components, using grounded capacitors. The filters are mapped on the FPAA, and both architectures are validated with simulations in LTspice using 90-nm complementary metal-oxide semiconductor (CMOS) technology. Both proposed FPAA and filters generalized synthetic method achieve simple, flexible, low-power designs for implementation of biopotential signal processing systems.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.770-773
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• 2002

Two sinusoidal voltage-controlled oscillators using linear operational transconductance amplifiers are presented in this paper: One is based on the positive-feedback bandpass oscillator model and the other on the negative-feedback Colpitts model. The bandpass VCO consists of a noninverting amplifier and a current-controlled LC-tuned circuit which is realized by two linear OTA's and two grounded capacitors, while the Colpitts VCO consists of an inverting amplifier and a current-controlled LC-tuned circuit realized by three linear OTA's and three grounded capacitors. Prototype circuits have been built with discrete components. The experimental results have shown that the Colpitts VCO has a linearity error of less than 5 percent, a temperature coefficient of less than rm 100 ppm/$^{circ}C$, and a $pm1.5 Hz $frequency drift over an oscillation frequency range from 712Hz to 6.3kHz. A total harmonic distortion of 0.3 percent has been measured for a 3.3kHz oscillation and the corresponding peak-to-peak amplitude was 1V. The experimental results for bandpass VCO are also presented.

• Journal of IKEEE
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• v.11 no.3
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• pp.122-128
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• 2007

Sinusoidal voltage-controlled oscillators (VCOs) based on Colpitts and Hartley oscillators are presented. They consist of a LC parallel-tuned circuit connected in a negative-feedback loop with an OTA-R amplifier and two diode limiters, where the inductor is simulated one realized with temperature-stable linear operational transconductance amplifiers (OTAs) and a grounded capacitor. Prototype VCOs are built with discrete components. The Colpitts VCO exhibits less than 1% nonlinearity in its current-to-frequency transfer characteristic from 4.2 to 21.7 MHz and ${\pm}$95 ppm/$^{\circ}C$ temperature drift of frequency over 0 to $70^{\circ}C$. The total harmonic distortion (THD) is as low as 2.92% with a peak-to-peak amplitude of 0.7 V for a frequency-tuning range of 10.8-32 MHz. The Hartley VCO has the temperature drift and THD of two times higher than those of the Colpitts VCO.