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

• Transactions on Electrical and Electronic Materials
• /
• v.18 no.5
• /
• pp.257-260
• /
• 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 Electrical and Electronic Material Engineers
• /
• v.23 no.4
• /
• pp.267-272
• /
• 2010

In this paper, a Gm-C LPF utilizing common-mode feedforward (CMFF) CMOS inverter type operational transconductance amplifier (OTA) has been designed and verified by circuit simulations. The CMFF CMOS inverter OTA was optimized for wide input linearity and low current consumption using a standard 0.18 ${\mu}m$ CMOS process; gm of 100 ${\mu}S$ and current of 100 ${\mu}A$ at supplied voltage of 1.3 V. Using this optimized CMFF CMOS inverter type OTA, an elliptic 5th order Gm-C LPF for GPS specifications was designed. Gain and frequency tuning of the LPF was done by changing the internal supply voltages. The designed Gm-C LPF gave pass-band ripple of 1.6 dB, stop-band attenuation of 60.8 dB, current consumption of 0.60 mA at supply voltage of 1.2 V. The gain and frequency characteristics of designed Gm-C LPF was unchanged even though the input common-mode voltage is varied.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.43 no.12 s.354
• /
• pp.81-88
• /
• 2006

This paper describes a new linear operational transconductance amplifier (OTA). To improve the linearity of the OTA, we employ a mobility compensation circuit that combines the transistor paths operating at the triode and subthreshold regions. The common-mode control schemes consist of a common-mode feedback (CMFB) and common-mode feedforward (CMFF). The circuit enhances linearity of the transconductance (Gm) under the wide input voltage swing range. The proposed OTA shows ${\pm}1%$ Gm variation and the total harmonic distortion (THD) of below -73dB under the input voltage swing range of ${\pm}1.1V$. The OTA is implemented using a $0.35{\mu}m$ n-well CMOS process under 3.3V supply.

• Journal of the Korean Institute of Telematics and Electronics C
• /
• v.34C no.6
• /
• pp.51-57
• /
• 1997

Low-voltage, low-power gm-C filter utilizing newly dveloped operational transconductance amplifier (OTA) is described in this paper. The OTA has only two MOS transistors in saturation region between $V_{DD}$ and GND, and thus low voltage operation is possible. To improve the linearity, the OTA is made differential. Common mode feedback, essential in differential circuit, requires no additional implemented in $0.8\mu\textrm{m}$ CMOS process, and the center frequency can be controlled from 15MHz with 3.0V single power supply.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.15 no.3
• /
• pp.326-333
• /
• 2015

This paper reports an adaptive positive feedback bias control technique for operational transconductance amplifiers to adjust the bias current based on the output current monitored by a current replica circuit. This technique enables operational transconductance amplifiers to quickly adapt their power consumption to various analog workloads when they are configured with negative feedback. To prove the concept, a test voltage follower is fabricated in $0.5-{\mu}m$ CMOS technology. Measurement result shows that the power consumption of the test voltage follower is approximately linearly proportional to the load capacitance, the signal frequency, and the signal amplitude for sinusoidal inputs as well as square pulses.

• Proceedings of the KIEE Conference
• /
• 1990.07a
• /
• pp.525-528
• /
• 1990

In this paper, a CMOS Operational Transconductance Amplifier (OTA) which is used for high-frequency operation has been designed and simulated by SPICE 2G program. To increase input linear range, the input stage is designed by cross-coupled pair. And the output stage insert buffer stage for the buffing and gain. The band-width of designed OTA is $50{\sim}60$ [MHz].

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.5 no.3
• /
• pp.168-172
• /
• 2005

In this paper, we present a new adaptive biasing scheme for CMOS op-amps. The designed circuit has been used in an Operational Transconductance Amplifier (OTA) with ${\pm}1$ V power supply, and it has improved the positive and negative slew rates from 2.92 V/msec to 1242 V/msec and from 1.56 V/msec to 133 V/msec respectively, while maintaining all the small-signal performance parameter values the same as that without adaptive biasing (as expected), however, there was a marginal decrease of the dynamic range. The most useful features of the proposed circuit are that it uses a very low number of components (thus not creating severe area penalty) and requires only 25 nW of extra stand-by power.

• ETRI Journal
• /
• v.31 no.5
• /
• pp.576-584
• /
• 2009

A novel tunable transconductor is presented. Input transistors operate in the triode region to achieve programmable voltage-to-current conversion. These transistors are kept in the triode region by a novel negative feedback loop which features simplicity, low voltage requirements, and high output resistance. A linearity analysis is carried out which demonstrates how the proposed transconductance tuning scheme leads to high linearity in a wide transconductance range. Measurement results for a 0.5 ${\mu}m$ CMOS implementation of the transconductor show a transconductance tuning range of more than a decade (15 ${\mu}A/V$ to 165 ${\mu}A/V$) and a total harmonic distortion of -67 dB at 1 MHz for an input of 1 Vpp and a supply voltage of 1.8 V.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.46 no.1
• /
• pp.92-97
• /
• 2009

Low power consumption is crucial for medical implantable devices. A low-power 4th-order band-pass Gm-C filter with distributed gain stage for the sensing stage of the implantable cardiac pacemaker is proposed. For the implementation of large-time constants, a floating-gate operational transconductance amplifier with current division is employed. Experimental results for the filter have shown a SFDR of 50 dB. The power consumption is below $1.8{\mu}W$, the power supply is 1.5 V, and the core area is $2.4\;mm{\times}1.3\;mm$. The filter was fabricated in a 1-poly 4-metal $0.35-{\mu}m$ CMOS process.