Small-signal Equivalent Circuit Parameters Research Articles

Simulation studies of a 2 Gb s−1 monolithic integrated smart pixel based on fabricated p-i-n PD, DHBT and a VCSEL

A smart pixel that can function as a building block of an optical transceiver with circular dimensions is proposed using InGaP/GaAs double heterojunction bipolar transistors (DHBTs) and a GaAs/AlGaAs vertical cavity surface emitting laser (VCSEL). Fabricated DHBT showed a breakdown voltage of 13 V and a cut-off frequency of 35 GHz at Ic = 30 mA. Also a high-performance 850 nm infra-red VCSEL exhibited a threshold current of 3.5 mA with a maximum optical output of 4.8 mW at Ic = 20 mA and forward voltage of 1.8 V. The detector, comprised of the base-to-collector junction of the DHBT as a pin-PD, produced a photocurrent of 180 µA for a given input power of 0.3 mW. The extracted small-signal equivalent circuit parameters from measurement of these devices were used in PSPICE simulations to design an interface drive circuit for high-speed modulation. The overall OEIC circuit performance operates up to data rates of 2 Gb s−1 at 1 mW output power with maximum output voltage of 2 V across the VCSEL and modulation current of 5 mA.

Numerical and experimental study of a 0.25 µm fully-depleted silicon-on-insulator MOSFET: static and dynamic radio-frequency behaviour

We investigate the static and dynamic characteristics of a 0.25 µm gate-length fully-depleted silicon-on-insulator metal–oxide–semiconductor field effect transistor. Considering properly the physical topology of the transistor with its accesses, numerical simulations are performed using a two-dimensional ensemble Monte Carlo simulator and these are compared with experimental results. Moreover, in the simulation we include important effects that appear in real transistors, such as surface charges, contact resistances, impact ionization phenomena and extrinsic parasitic capacitances. The appearance of a velocity overshoot region near the drain, together with the presence of hot carriers in the channel, is observed in the saturation regime. The dynamic behaviour of the device is described through significant small signal equivalent circuit parameters, which are examined by means of internal quantities (such as profiles of the internal electron concentration), provided by numerical simulations. In general, the device shows excellent performance in terms of important design parameters, such as transconductance-to-current ratio, transconductance and cut-off frequency together with a reduced capacitive coupling to the substrate. The results of the Monte Carlo simulations show an exceptional agreement with the experimental data, thus confirming the validity of the simulator as a reliable tool for the analysis of the influence of geometrical and electrical parameters on the static and dynamic performance of the device.

Small signal and power measurements of AlGaN/GaNHEMTwith SiN passivation

Small signal S-parameters and loadpull measurements are reported for AlGaN/GaN HEMT devices with 200 nm SiN passivation. The maximum output power increases from 0.59 W/mm to 1.45 W/mm and the efficiency is also enhanced from 16 to 27% for 2×50 µm HEMT devices after SiN passivation. Small signal equivalent circuit parameters including parasitic and intrinsic ones have been extracted from the measured S-parameters and are used to explain the effect of SiN on the power characteristics.

Low temperature analysis of 0.25 μm T-gate strained Si/Si/sub 0.55/Ge/sub 0.45/ n-MODFET's

A low temperature dc and HF investigation of 0.25 /spl mu/m T-gate Si/Si/sub 0.55/Ge/sub 0.45/ n-MODFET's is presented. Outstanding maximum oscillation frequencies f/sub max/ range from 100-120 GHz at 300 K up to 195 GHz at 50 K. These high-frequency characteristics are the first reported at low temperature on Si/SiGe n-MODFET's and are also the highest room temperature data reported so far; physical modeling is used to explain the main trends observed when cooling down the n-MODFET. Many experimental data are presented. The dependence on temperature and biases of the important small-signal equivalent circuit parameters is investigated to analyze the device high-frequency performances and the minimum noise figure of the intrinsic device is determined.

Extraction of high-frequency equivalent circuit parameters of submicron gate-length MOSFET's

As the effective gate-length of a MOSFET reduces, its high-frequency characteristics improve. However, they become more difficult to model. Current SPICE models are based on DC measurement data and simplistic capacitance models which can only approximate the high-frequency device characteristics up to a fraction of the device unity current gain frequency (f/sub /spl tau//). Thus, it is important to investigate the high-frequency characteristics and then incorporate the small-signal equivalent circuit parameters in SPICE. In this, work we report a simple nonquasi static model, which offers good accuracy needed for circuit simulation, and a new curve fitting method for the extraction of the network model elements. The current work is part of a study aimed at improving the existing scalable model for MOSFET's, and it focuses on extracting the elements of an equivalent circuit which describes the state-of-the-art device.

Accurate de-embedding technique for on-chip small-signal characterization of high-frequency optical modulator

A simple and accurate de-embedding technique has been developed for characterizing the microwave circuit behavior of noninsertable multiple quantum well waveguide modulators with on-chip two-port S-parameter measurements. The small signal equivalent circuit parameters extracted from the error corrected modulation response show an excellent agreement with both one-port microwave reflection coefficient measurement and CV data measured at 1 MHz.

Analytical method for determining equivalent circuit parameters of GaAs FETs

An analytical method has been developed that gives a simple and practical means of extracting small-signal equivalent circuit parameters (ECPs) of GaAs FETs with negligibly small bond-pad capacitances. Only the S-parameter measurement of the pinched-off cold field-effect transistor (FET) is enough to determine the extrinsic FET ECPs. The intrinsic FET ECPs of a medium-power Ku-band GaAs FET chip with a total gate width of 800 /spl mu/m have been analytically extracted for two types of eight-element intrinsic FET models; Model 1 (Curtice model) and Model 2 that differ in the control voltage (V/sub G/) definition. Model 2 with V/sub G/ defined across the gate-source capacitance is found more appropriate judging from the smaller frequency dependence of the ECPs and a better agreement between the calculated and measured S-parameters over 2-20 GHz.

Analytical parameter extraction of the HBT equivalent circuit with T-like topology from measured S-parameters

A pure analytical method for extraction of the small-signal equivalent circuit parameters from measured data is presented and successfully applied to heterojunction bipolar transistors (HBT's). The T-like equivalent circuit is cut into three shells accounting for the connection, and the extrinsic and intrinsic parts of the transistor. The equivalent circuit elements are evaluated in a straightforward manner from impedance and admittance representation of the measured S-parameters. The measured data are stripped during the extraction process yielding, step by step, a full set of circuit elements without using fit methods. No additional knowledge of the transistor is needed to start the extraction process with its self-consistent iteration loop for the connection shell. The extrinsic and intrinsic equivalent circuit elements are evaluated using their bias and frequency dependencies. This method yields a deviation of less then 4% between measured and modeled S-parameters. >

Determination of the small-signal parameters of an AlGaAs/GaAs MODFET

The small-signal equivalent-circuit parameters of an AlGaAs/GaAs MODFET are derived by a first-order perturbation around the two-region DC model of a FET. For the first time the contribution of the AlGaAs electrons is included by using an accurate charge-control model. The charge-control model uses mixed quantum mechanical and classical approach to determine the density of channel electrons and AlGaAs neutral donors as a function of rate voltage. The model predictions show good agreement with experimental results for both low and high drain bias voltages.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Thermal dilution: instrumentation with thermistors.

Based on the steady-state small-signal equivalent circuit parameters for a self-heated thermistor, the relationship of flow versus temperature sensitivity is found to be linear with the power dissipated in the thermistor. For the thermistors considered (YSI 520 and 512 series) flow sensitivity is negligible at power inputs below .01 mw. This power applied to a thermistor incorporated into a balanced Wheatstone bridge provides an output signal of approximately 150 μv for a .1 C temperature change. Amplifier requirements for thermal dilution are: gain of 104, a frequency response of 25 cycle/sec or greater, and a peak noise referred to input of less than 2 μv. A calibration procedure using a fixed resistance bridge unbalance and calculations from measured thermistor parameters is discussed. The procedure is independent of changes in amplifier and recorder gain, or changes in bridge voltage and ambient temperature. The effect of thermistor aging on the procedure is considered and found to be quite small. A bridge circuit incorporating variable bridge voltage is described and the application of the variable bridge voltage to the in vivo estimation of the thermistor dissipation constant and flow effects are discussed. Intravascular temperature measurements in man and in the anesthetized dog indicate that changes in thermistor resistance periodic with pulse are primarily the result of intermittent contact of the thermistor with the vessel wall, and due to changes in both temperature and dissipation constant. temperature measurement; cardiac output Submitted on June 12, 1964