KEYWORDS: Amplifiers, Signal detection, Sensors, Linear filtering, Optical amplifiers, Optoelectronics, Interference (communication), CMOS sensors, Signal to noise ratio, Phase shifts
We have designed dual lock-in amplifier (LIA) circuits in 0.18 μm CMOS technology for antibody-antigens
(IgG) detection using optoelectronics. The purpose of this work is to develop a lock-in amplifier integrated circuit (IC)
using the dual phase scheme that detect the phase difference between the input signal and the reference signal although a
phase shifter is absent. Our LIA consist of high gain amplifier, signal amplifier, and phase sensitive detection. Amplifier
structure is based on two-stage differential operational amplifier (op-amp) with RC Miller compensation technique. By
using the RC Miller compensation technique, we obtain 60° the phase margin of the op-amp. Here, the resistor works for
increasing the unit gain bandwidth and the capacitor works for increasing the phase margin. The lock-in amplifier
consume 8.6 mA from a 1.8 V supply.
KEYWORDS: Signal detection, Interference (communication), Linear filtering, Biosensors, Switches, Sensors, Modulation, Signal to noise ratio, Photodetectors, Amplifiers
Recently, a number of portable biosensors have been developed to check the health condition of human beings
regardless of time and place. Though those sensors have a merit of a handy one, the signals are inevitably measured with
intensive background noises. In order to detect a weak signal concealed in intensive background noises such as Johnson
noise, 1/f noise, and shot noise, a special technique is essentially required. As of a special technique, the lock-in
detection method is able to minimize the effects of these noises using modulated signal and reference signals. Previously,
we applied the lock-in detection method to infrared detection system. The sensitivity of this system was decided by the
1/f noise at the photodetector. In this work, we have demonstrated the portable bio-sensor system using high frequency
infrared laser diode and photodetector. Therefore, the main signal of interest may keep away from the effect of the 1/f
noise with hybrid-type highly sensitive lock-in detection module. This technique provides the minimum detection range
of 3 mV and the dynamic range of 25.8 dB at the noise level of 120 mV.
Portable bio-optical systems have required not only small size but also high sensitive and precise detection technique.
To achieve high sensitivity, portable bio-optical systems should be set up to minimize the effects of noises such as
Johnson noise, 1/f noise, shot noise etc. In order to reduce the influence from these noises, we have applied a novel lock-in
detection technique. The lock-in detection technique is able to effectively suppress these noises as choosing a
frequency high enough to avoid 1/f noise and low enough to avoid parasitic noises occurred on high frequency. We use
lock-in detection technique with a simple structure - several op-amplifiers and MOSFETs. Using the lock-in scheme, we
recovered signals in the presence of overwhelming background noises without applying multistage amplifiers and filters.
This technique provides high resolution measurements of relatively clean signals over several orders of magnitude and
frequency by compared with conventional detection method. We have demonstrated portable bio-optical system using
infrared LED and PD with our hybrid type lock-in detection module.
The lasing characteristics of three-guide coupled ring lasers using the self-aligned total internal reflection
(TIR) mirrors were investigated numerically and experimentally. The rectangular laser cavity consists of four low loss
TIR mirrors and an output coupler made out of passive three coupled waveguides. Two different lasers having active
section lengths of 250 and 350 μm and total cavity lengths of 580 and 780 μm are fabricated. For both devices lasing
thresholds of 38 mA is obtained at room temperature and under CW operation. Lasing is predominantly single mode
with the side mode suppression ratio better than 20 dB.
KEYWORDS: Resonators, Signal to noise ratio, Refractive index, Waveguides, Optical microcavities, Sensors, Biosensors, Signal detection, Data acquisition, LCDs
We have demonstrated a novel bio-signal processing technique with hybrid bio-systems using an optical microcavity
ring resonator. The intensity of the transmitted light through the ring resonator has a periodic and sensitive region
depending on the wavelength of the incident light into the ring resonator. It is possible to detect biomolecules with the
ring resonator, because the resonance profile is shifted by refractive index changes due to an amount of biomolecules on
the surface of sensing areas. Our processing technique is based on using dual-wavelength. In this scheme, high accuracy
can be achieved by comparing the intensity of two incident lights which has channel spacing of the half period of the
sensitive region. More detailed experimental results on a novel bio-signal processing technique will be presented.
We developed a CMOS-based trans-impedance amplifier (TIA) circuits for analog optical
communication systems. Our TIA structure is based on common-source configuration and a novel functional
active load (FAL). Proposed FAL structure is composed the two PMOSs that have the symmetric structure. In
those schemes, transfer curve of TIA can be tuned by the gate voltage of FAL in the way to improve linearity.
In analog optical transceiver, TIA employing the FAL can suppress the nonlinearity originated from various
sources. Because the nonlinearity deteriorate analog communication systems, enhancement of linearity is
crucial to improve the analog transceiver performances. In this work, we have designed the TIA with FAL in a
0.18 &mgr;m CMOS technology. The linearity of TIA is controlled by the variation of transfer curve with the
change of the FAL bias voltage. As of the simulation results, the IIP3 level of the TIA employing FAL is
enhanced by about 3.393 dB with the Vg variation in FAL.
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