• Proceedings of the IEEK Conference
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• 2001.06e
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• pp.185-188
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• 2001

This paper proposes an error amplifier circuit using OTA(Operational Transconductance Amplifier) which is the main constituent element in pulse width modulation circuit. The proposed OTA error amplifier circuit is featured by simple circuit configuration, excellent high frequency characteristics and bias current controlled output. Through the experiment of pulse width modulation circuit, the validity of the operation of the OTA error amplifier circuit is verified.

• 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.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.12
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• pp.54-62
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• 2003

A systematic synthesis process is described lot the simulation of current-controllable inductors using operational transconductance amplifiers (OTAs). The process is used to obtain three circuits; two are believed It) be novel. The process is also applied to design current-controllable frequency-dependent negative resistances (FDNRs). Operation principles of designed circuits are presented and experimental results are used to verify theoretical predictions. The results show close agreement between predicted behavior and experimental performance. The application of a FDNR to a current-controllable band-pass filter is also presented.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.12
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• pp.59-65
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• 1998

In this paper, a novel rail-to-rail input stage circuit with improved transconductance Is designed. Its excellent performances over whole common-mode input voltage Vcm range is demonstrated by circuit simulator HSPICE. The novel input stage circuit comprises additional 4 input transistors and 4 current sources/sinks. It maintains DC currents of signal amplifying transistors when one of the differential input stage circuits operates, but it reduces these currents to 1/4 when both differential input stage circuits operates, As a result, a operational amplifier with the novel circuit maintains nearly constant transconductance performance and unity-gain frequency in strong inversion region. The novel circuit allows an optimal frequency compensation and uniform operational amplifier performance over whole Vcm range.

• Transactions on Electrical and Electronic Materials
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• v.18 no.5
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• pp.257-260
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• 2017

In this paper, we present the design of a 4.5 V low dropout (LDO) voltage regulator implemented in the 130 nm CMOS process. The design uses a two-stage cascaded operational transconductance amplifier (OTA) as an error amplifier, with a body bias technique for reducing dropout voltages. PMOS is used as a pass transistor to ensure stable output voltages. The results show that the proposed LDO regulator has a dropout voltage of 32.06 mV when implemented in the130 nm CMOS process. The power dissipation is only 1.3593 mW and the proposed circuit operates under an input voltage of 5V with an active area of $703{\mu}m^2$, ensuring that the proposed circuit is suitable for low-power applications.

• 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.

• 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.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.1
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• pp.59-67
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• 2016

A novel instrumentation amplifier (IA) using fully-differential linear operational transconductance amplifier (FLOTA) for electronic measurement systems with low cost, wideband, and gain control with wide range is designed. The IA consists of a FLOTA, two resistor, and an operational amplifier(op-amp). The principal of the operating is that the difference of two input voltages applied into FLOTA converts into two same difference currents, and then these current drive resistor of (+) terminal and feedback resistor of op-amp to obtain output voltage. To verify operating principal of the IA, we designed the FLOTA and realized the IA used commercial op-amp LF356. Simulation results show that the FLOTA has linearity error of 0.1% and offset current of 2.1uA at input dynamic range ${\pm}3.0V$. The IA had wide gain range from -20dB to 60dB by variation of only one resistor and -3dB frequency for the 60dB was 10MHz. The proposed IA also has merits without matching of external resistor and controllable offset voltage using the other resistor. The power dissipation of the IA is 105mW at supply voltage of ${\pm}5V$.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.11
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• pp.1274-1281
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• 1988

A new voltage-controlled oscillator based on a voltage-controlled integrator has been developed. It consists of a Schmitt-trigger and a voltage-controlled integrator, which is realized by an operational transconductance amplifier (OTA) and a grounded capacitor. The input control voltage changes the time constant of the integrator, and hence the oscillation frequency. The SPICE simulation shows that a prototype circuit, which oscillates at 12.21 KHz at 0 V, has the conversion sencitivity 2,437 Hz/V and the residual nonlinearity less than 0.68% in a control voltage range from -2 V to 2 V. It also shows that the circuit provides a temperature drift less than + 250 ppm/$^{\circ}$C for frequencies up to 100 KHz.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.7 no.1
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• pp.40-44
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• 2014

A bridge resistance deviation-to-period (BRD-to-P) converter is presented for interfacing resistive biosensors. It consists of a linear operational transconductance amplifier (OTA) and a current-controlled oscillator (CCO) formed by a current-tunable Schmitt trigger and an integrator. The free running period of the converter is 1.824 ms when the bridge offset resistance is $1k{\Omega}$. The conversion sensitivity of the converter amounts to $3.814ms/{\Omega}$ over the resistance deviation range of $0-1.2{\Omega}$. The linearity error of the conversion characteristic is less than ${\pm}0.004%$.