• 대한의용생체공학회:의공학회지
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• 제2권1호
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• pp.55-64
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• 1981

The important parameters of DC amplifier, which is widely use4 for the medical and engineering fields, are input offset voltage and temperature drift. Chopping amplifier reduces approximately 10% the parameters changing than monolithic operational amplifier. In this study, a chopping amplifier with semiconductor chopper is designed and tested, this chopper is realized by CMOS analog switch and timing circuits. The test results approve that designed amplifier is suitable for precision instrument DC amplifier.

• 전기의세계
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• 제18권5호
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• pp.12-19
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• 1969

The sensitivity of transistorized d.c. amplifiers is mainly limited by drift at operating point caused by ambient temperature changes. A chopper-type transistorized amplifier is necessary to obtain a high sensitivity without recourse to drift compensation which requires the adjustment of several balancing controls. A chopper-stabilized system consisting of an electro-mechanical chopper for input and output and a high-gain a.c. amplifier is designed and analyzed. The gain of the a.c. amplifier, expressed as the ratio of voltages, is larger than 80db in the band of 50C/S - 100KC/S. The complete system gives an open-loop gain of 68db at direct current. The offset voltage is 20.mu.V referred in input and the voltage drift at the input is less than 10.mu.V/hr at 25.deg.C. This type of amplifier would be useful for the high-gain transistorized d.c. amplifier for analog computers. Also, due to the high input impedance, it is suitable for amplification of signals from wide range of source impedances.

• 전자공학회논문지
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• 제53권10호
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• pp.27-33
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• 2016

본 논문은 초퍼 안정화기법을 적용한 저잡음 증폭기를 제안한다. 초퍼 안정화기법은 CMOS 증폭기의 저주파수 대역 오프셋과 플리커 잡음을 감소시키는 효과적인 기법이다. 기존의 초퍼 증폭기는 초퍼로 인해 발생되는 초핑 스파이크를 제거하기 위해 Low Pass Filter(LPF)를 사용하기 때문에 저항과 커패시터가 큰 면적을 차지한다는 단점을 가지고 있다. 제안된 초퍼 증폭기는 LPF 대신 샘플 앤 홀드 방식의 초핑 스파이크 제거 회로를 사용하여 적은 전압감쇄에서 36%, 면적에서 11%의 이득을 얻을 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.483-484
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• 2007

In this paper, we describe a chip design technique for instrumentation amplifier using a nested-chopping technique. Conventional chopping technique uses a pair of chopper, but nested chopping technique uses two pairs of chopper to reduce residual offset and 1/f noise. The inner chopper pair removes the 1/f noise, while the outer chopper pair reduces the residual offset. Our instrumentation amplifier using a nested chopping technique has residual offset under 100 nV. We also implement very low frequency filter. Since this filter needs very large RC time constant, we use a technique named 'diode connected PMOS' to increase R with small die area. The total power consumption is 3.1 mW at the supply voltage of 3.3V with the 0.35um general CMOS technology. The die area of implemented chip was $530um{\times}300um$.

• 대한전자공학회논문지
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• 제12권2호
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• pp.43-46
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• 1975

쵸퍼형DC증폭기의 AC증폭기의 인력신호는 일련의 단형연이다. 따라서 이 때의 AC증폭기의 동작은 정장파신호에 대한 그것과 큰 차이가 있다. 본 논문은 단형파에 대한 AC증폭기의 각단에서의 파형의 찌그러짐에 대한 해석을 하여 쵸퍼용AC증폭기의 설계상의 문제점을 고찰한 것이다. 각증폭단의 시정수가 동일한 경우에는 각단의 신호파형은 모두 지수감쇠속형파로 되며, 시정수가 다를 경우에는 여러개의 지수감쇠구형파의 합성파로 된다. In a chopper amplifier the input signal of the AC amplifier is a train of square-waves. In the rase of square-wave the operatiom of AC amplifier is much different from that of ordinary sinusoidal wave. In this paper for the purpose of contributing to the design of chopper amplifier destortions of waveforms in the amplifier were investigated. When the time constant of each stage is equal the waveform in each stave apppears as square wave whose top is exponentially decaying. And when each stave has different time constant the waveform in n-th stage is composed of n-square waves whose tops are exponentially decaying.

• 센서학회지
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• 제31권2호
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• pp.120-124
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• 2022

With advancements in underwater stealth technology for naval vessels, new sensor configurations for detecting targets have been attracting increased attention. Latest underwater mines adopt multiple sensor configurations that include electric field sensors to detect targets and to help acquire accurate ignition time. An underwater electric field sensor consists of a pair of electrodes, signal processing unit, and preamplifier. For detecting underwater electric fields, the preamplifier requires low-noise amplification at ultra-low frequency bands. In this paper, the specific requirements for low-noise preamplifiers are discussed along with the experimental results of various setups of matched transistors and chopper stabilized operational amplifiers. The results showed that noise characteristics at ultra-low frequency bands were affected significantly by the voltage noise density of the chopper amplifier and the number of matched transistors used for differential amplification. The fabricated preamplifier was operated within normal design parameters, which was verified by testing its gain, phase, and linearity.

• 센서학회지
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• 제23권3호
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• pp.165-169
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• 2014

An existing infrared (IR) analysis system is generally composed of infrared source, IR focusing lenses, IR detector, and optical chopper. An optical chopper is widely used in combination with lock-in amplifier to improve the signal-to-noise ratio by periodically interrupting incident light beam. During recent years, a few researches on miniaturized optical chopper have been reported to apply to micro-scaled optical systems. In this paper, a micro optical chopper operated by electromagnetic actuation is proposed and applied to a miniaturized micro-scaled optical system operating in IR spectral range. Additionally, the fabrication method of the proposed micro chopper is demonstrated. The proposed micro optical chopper is composed of the polydimethylsiloxane (PDMS) membrane, solenoid, and permanent magnet. The permanent magnet is bonded on the PDMS membrane using an ultraviolet-activated adhesive. The operation of the chopper is based on the attractive and repulsive forces between permanent magnet and solenoid induced by an electrical current flowing through the solenoid. The fabricated micro optical chopper could operate up to 200 Hz of frequency. The maximum operating distance of the chopper with 7mm diameter membrane was $750{\mu}m$ at 100 Hz of frequency.

• Journal of Semiconductor Engineering
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• 제2권1호
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• pp.109-118
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• 2021

This review paper describes the overall operating principle of a discrete-time delta-sigma modulator (DTDSM) and a continuous-time delta-sigma modulator (CTDSM) using a switched-capacitor (SC). In addition, research that has solved the problems related to each delta-sigma modulator (DSM) is introduced, and the latest developments are explained. This paper describes the chopper-stabilization technique that mitigates flicker noise, which is crucial for the DSM. In the case of DTDSM, this paper addresses the problems that arise when using SC circuits and explains the importance of the operational transconductance amplifier performance of the first integrator of the DSM. In the case of CTDSM, research that has reduced power consumption, and addresses the problems of clock jitter and excess loop delay is described. The recent developments of the analog front end, which have become important due to the increasing use of wireless sensors, is also described. In addition, this paper presents the advantages and disadvantages of the three-opamp instrumentation amplifier (IA), current feedback IA (CFIA), resistive feedback IA, and capacitively coupled IA (CCIA) methods for implementing instrumentation amplifiers in AFEs.

• 전자공학회논문지B
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• 제31B권9호
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• pp.67-75
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• 1994

In this paper, we manufactured the continuum receiver system for observing the continuum waves emitted from the continuum sources with using the 14m radio-telescope. The receiving system measures the total power of the continuum sources and consists of DC-amplifier, beam-chopper system. Phase-Locked Loop(PLL) circuit, blanking circuit and its period selection circuit, V/F converter, and counter part which are capable of interfacing with the computer which is used for a data acquisition and making the radio-telescope track the source. We compared the obsevation results which use the existing DVM method with the observation results which use the continuum receiver to measure the total power of the sources. Moreover, by method of beam switching observation which uses newly installed beam chopper system. We can significantly improve the observational efficiency more than the existing position switching observation method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.569-574
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• 1998

This paper presents a two-paralleled 4 quadrant DC chopper type PWM power conversion circuit in order to generate a gradient magnetic field in the Magnetic Resonance Imaging (MRI) system. This power amplifier is connected in parallel with the conventional 4-quadrant DC chopper using IGBTs at their inputs/outputs to realize further high-power density, high speed current tracking control, and to get a low switching ripple amplitude in a controlled current in the Gradient Coils (GCs). Moreover, the power conversion circuit has to realize quick rise/fall response characteristics in proportion to various target currents in GCs. It is proposed in this paper that a unique control scheme can achieve the above objective. DSP-based control systems realize a high control facility and accuracy. It is proved that the new control system will greatly enlarge the diagnostic target and improve the image quality of MRI.