High Frequency Analog Research Articles

A very high-frequency CMOS complementary folded cascode amplifier

A wide-band, fast settling CMOS complementary folded cascode (CFC) transconductance amplifier for use in analog VLSI high frequency signal processing applications is introduced. The superior performance of the CFC architecture over that of the folder cascode (FC) or mirrored cascode (MC) approaches for VLSI amplifiers is demonstrated. The symmetrically configured complementary input stage provides a wide common-mode input voltage range. The amplifier performs as an operational transconductance amplifier (OTA) and displays a first-order dominant pole when loaded by a shunt capacitor. The transconductance amplifier is small in area (0.016 mm/sup 2/), and well suited for high frequency analog signal processing applications. Simulation and experimental results demonstrate a DC gain of approximately 50 dB, with a 0.1% settling response of under 10 ns for loads varied from 0 to 2 pF. >

Small signal nonquasistatic models for GaAs field effect transistors for implementation in SPICE. Part 1: Modulation-doped field effect transistors (MODFETs)

A general small signal nonquasistatic model for modulation doped field effect transistors (MODFETs) is presented. The model is valid for devices operating in both linear and saturation regions. The two dimensional electron gas (2DEG) current is modelled. The current flowing in the parasitic doped AlGaAs layer is considered elsewhere. In both cases, admittance parameters (Y-parameters) are derived and used to build SPICE-like equivalent circuits. The proposed model can, therefore, be easily implemented in SPICE for microwave and high frequency analogue circuit analysis. The results show that, for a 1 μm gate length MODFET, the error is less than 5% at 86 GHz.

Optical detectors: research to reality

In many applications where either high frequency analogue or digital signals, or short duration pulses are present, advantages of replacing conventional RF and microwave components by optical ones are well known. For example, the use of fibre-optics offers an interface-free technology which is lighter, more compact and reliable, and an give a higher transmission bandwidth that its predecessors – important features for both present and future more complex systems. Unfortunately, adoption of this new technology has been delayed by problems in producing opto-electronic components which can operate at the relevant microwave frequencies. Recent improvements in materials and fabrication expertise and better under standing of the operating characteristics of these devices, however, seem finally to have brought them into the marketplace.

Particle-free wafer cleaning and drying technology : H. Mishima, T. Yasui, T. Mizuniwa, M. Abe and T. Ohmi. IEEE Trans. Semicond. Mfg2(3), 69 (1989)

Using SiSiGe heteroepitaxy grown by solid-sources (SS) molecular beam epitaxy (MBE) on LOCOS-patterned wafers, an n-p-n Si/SiGe/Si heterojunction bipolar transistor (HBT) which is isolated by a polysilicon-filled trench has been fabricated. Unlike other SiGe HBTs using a metallic salicide process, in this proposed device a titanium disilicide (TiSi2) base electrode layer is formed by deposition and patterning of an amorphous TiSi2.x (x = 0–0.9) layer on the SiGe base layer using selective wet etching. In view of a lower thermal budget furnace annealing at 840°C has only been applied for the drive-in and activation of arsenic (As) implanted in the polysilicon-emitter. The Si/Si0.85Ge0.15/Si n-p-n HBT with a 1 × 4 μm2 mask size emitter typically shows a common-emitter current gain of 118, an Early voltage in the range of 150–170 V, a breakdown voltage BVceo of 7.8 V, a unity current gain frequency fT of 20 GHz, and a maximum oscillation frequency fmax of 15 GHz. Considering the theoretical limit of fT vs BVceo, the performance of our device is near the limit and demonstrates a potential for high frequency analog IC applications.

Modeling of the MOS transistor for high frequency analog design

A high-frequency (HF) small-signal model is presented that is capable of describing accurately the MOS transistor (in saturation) at frequencies beyond the cutoff frequency. The model is carefully compared to other models. It is shown how all the circuit elements of the model can be measured. This measurement method uses S-parameter measurements, computer-controlled calibration techniques of the test setup and network analyzer, mathematical transformations of the S-parameters to other linear parameters, and extraction routines to fit the data towards the HF model. The model is finally used in the design of an HF optical transconductance amplifier to prove that this model is much more accurate than the classical models at higher frequencies. >

High-frequency analog modulation of a semiconductor laser

An investigation was made of high-frequency characteristics of GaAlAs injection lasers under continuous modulation conditions. The optical amplitude–frequency characteristics and the frequency dependence of the impedance made it possible to determine the equivalent circuits of two forms of lasers: a stripe laser and a laser with a channel in the substrate, which made it possible to optimize the input circuits of a laser light emitter. It was found that the channel-type laser had a highly linear modulation characteristic.

Problems and prospects of compound semiconductor field-effect transistors

The application of binary, ternary, and quaternary semiconducting III– V compounds for high frequency field-effect transistors (FETs) and microwave integrated circuits (ICs) presents hitherto unavailable options and challenging problems which arise from the inherent bulk and surface properties of these materials and of the interfaces between them and metal or dielectric overlayers. Although the depletion-mode (normally-on) Schottky barrier gate GaAs transistor is the older and, at this stage, more advanced technology, alternative approaches based primarily on insulated gate FETs and other materials such as InP, InxGa1−xAs, and InxGa1−xAsyP1−y have been demonstrated to have important advantages for enhancement type (normally-off) as well as depletion- and inversion-mode insulated gate FETs, a potential high frequency analog of the lower frequency silicon MOS technology. The problems and prospects of such devices and structures as well as those of a variety of Schottky barrier gate and heterojunction gate transistors will be discussed in terms of their surface and interface properties.

Resonant Impedance and Effective Series Resistance of High-Frequency Parallel Resonant Circuits

The writer has already published in a previous issue of the PROCEEDINGS a new method of measuring resonant impedance and radio-frequency resistance as applied to broadcast frequencies. In the present paper he gives, as another example of its application, some results obtained from the measurement in a band of high frequencies extending from 6300 to 26,300 kilocycles. It is ascertained that the additional dielectric loss, which is introduced into the resonant circuit by using a screen-grid tube as a dynatron, exercises only a slight influence on the measurement. The constants of the resonant circuit alone may be derived from those of the circuit combined with the tube, which can be measured directly. The correctness of the result is varified by the aid of a known value of the additional series resistance. Finally some remarks on short-wave amplification are given as a result of measurements.