Browsing by Subject "Transconductance"

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    AlGaN/GaN HEMT-based fully monolithic X-band low noise amplifier
    (Wiley, 2005-04) Schwindt, R.; Kumar, V.; Aktas, O.; Lee, J. W.; Adesida, I.
    A fully monolithic AlGaN/GaN HEMT-based low noise amplifier is reported. The circuit demonstrated a noise figure of 3.5 dB, gain of -7.5 dB, input return loss of -7.5 dB, and output return loss of -15 dB at 8.5 GHz. The dc characteristics of individual 0.25-μm × 150-μm transistors were: maximum current density of 1.0 A/mm, maximum transconductance of 170 mS/mm and a threshold voltage of -6.8 V. The devices have a typical short circuit current gain cutoff frequency of 24.5 GHz and a maximum oscillating frequency of 48 GHz. The devices demonstrated a minimum noise figure of 1.6 dB with an associated gain of 10.6 dB at 10 GHz.
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    AlGaN/GaN-Based laterally gated high-electron-mobility transistors with optimized linearity
    (IEEE, 2021-02-01) Odabaşı, Oğuz; Yılmaz, Doğan; Aras, Erdem; Asan, Kübra Elif; Zafar, Salahuddin; Çankaya Akoğlu, Büşra; Bütün, Bayram; Özbay, Ekmel
    In this work, highly linear AlGaN/GaN laterally gated (or buried gate) high-electron-mobility transistors (HEMTs) are reported. The effect of gate dimensions on source-access resistance and the linearity of laterally gated devices are investigated experimentally in detail for the first time. Transistors with different gate dimensions and conventional planar devices are fabricated using two-step electron beam lithography (EBL). Current-voltage, source-access resistance, small-signal, and two-tone measurements are performed to evaluate the linearity of devices. Contrary to conventional planar HEMTs, the intrinsic transconductance of laterally gated devices monotonically increases with increasing gate voltage, showing a similar behavior as junction field-effect transistors (FETs). The source-access resistance shows a polynomial increase with the drain current, which can be reduced by decreasing the filling ratio of the buried gates. Through the optimization of these two competing factors, i.e., intrinsic transconductance and the source-access resistance, flat transconductance with high linearity is achieved experimentally. The laterally gated structure shows flat transconductance and small-signal power gain over a larger span of gate voltage that is 2.5 times higher than a planar device. Moreover, 6.9-dB improvement in output intercept point (OIP3)/P DC is achieved. This approach can be used to improve the linearity of AlGaN/GaN HEMTs at the device level.
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    Analog CMOS implementation of cellular neural networks
    (1991) Baktır, İzzet Adil
    An analog CMOS circuit realization of cellular neural networks with transconductance elements is presented in this thesis. This realization can be easily adapted to various types of applications in image processing by just choosing the appropriate transconductance parameters according to the predetermined coefficients. The noise-reduction and edge detection examples have shown the effectiveness of the designed networks in real time image processing applications. For “fix function” cellular neural network circuits the number of transistors are reduced further by a new multi-input voltage-controlled current source.
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    Biquadratic transconductance switched-capacitor filters
    (IEEE, 1993-04) Tan, M. A.
    Switched-capacitor (SC) filters yield efficient implementations in integrated form. However, they employ op-amps, each of which must be designed for a given filter separately. Furthermore, SC filters are not tunable. This work presents a new type of sampled data filters consisting of transconductance elements, switches and capacitors, called transconductor switched capacitor (TSC) filters. Transconductance elements do not degrade their performance within a wide frequency range and tunable ones are available.
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    A reduction in the number of active components used in transconductance grounded capacitor filters
    (IEEE, 1990) Tan, Mehmet Ali; Schaumann, R.
    The number of active components in transconductance grounded capacitor filters is reduced. This reduction is possible in the case where capacitor loops and/or inductor cutsets exist in LC-ladder prototype. A more significant reduction is obtained in the OTA-C (operational transductance amplifier-capacitor version. The number of OTAs is reduced to 7 from 13 while the total capacitance value remains intact. It is also important to note that all transconductance elements or OTAs are identical except possibly one. The only drawback of this reduction is implementation of some floating capacitors instead of all grounded capacitors.