New non-quasi-static theory for extracting small-signal parameters applied to LDMOSFETs

Abstract

We present analytic formulas for simultaneously extracting the parasitic resistances, inductances, and the intrinsic parameters of a small-signal FET equivalent circuit model including the non-quasi-static (NQS) charging time-constants associated with the gate and drain charges, respectively. For the NQS equivalent circuit topology considered, there exists a continuum of solutions for the circuit parameters, as a function of the source resistance, giving exactly the same frequency response fit. A multi-bias analysis is used to determine the final source resistance. Realistic results are obtained for power LDMOSFETs despite the very small value of the parasitics in these power RF devices.Index Terms-FET equivalent circuits, LDMOSFET, microwave small-signal modeling, non-quasi-static, parameter extraction.

Non-Quasi-Static Large-Signal Model for RF LDMOS Power Transistors

“…Id (2) Qd (2) Quasi-Static parameter measurement data at multiple biases, through an automated numerical integration procedure. The model has a simple topology and can be conveniently implemented in any commercial circuit simulators.…”

“…Without the RC time constants and the resulting delay time, the simplified quasi-static model can lead to inaccurate results when the time constants are comparable to the inverse of excitation frequency. The majority of nonlinear electro-thermal models used to describe LDMOS transistors are based on quasi-static assumptions, and there have been previous research attempts to incorporate non-quasi-static effects in small-signal modeling [2] and large-signal modeling for 2.1 GHz application [3]. These modeling methods use additional nonlinear resistors and capacitors to represent the time delay and time constants, and complex model extraction procedure is usually required to obtain these component values.…”

RF electro-thermal modeling of LDMOSFETs for power-amplifier design

“…A two approximation can be made such that and . The microwave data is deembedded using the NQS multibias approach given in [14] and [15] to extract small-signal parameters and device parasitics. This involves fitting the extrinsic -parameters and then using analytical expressions for intrinsic and extrinsic parameters that are functions of -parameter fitting constants.…”

Isothermal DC and microwave characterizations of power RF silicon LDMOSFETs

“…Due to the high power which can be dissipated in these devices, of particular concern is the measurement and modeling of their electrothermal behavior [1]. For such modeling, isothermal microwave data are required to extract the FET model [2] and isothermal current-voltage ( -) data to determine the quiescent operating point of the device in the presence of self-heating and self-biasing. Under dc operation the dc and isothermal drain currents are related by with (1) where substrate temperature; average device temperature; effective thermal resistance; average power dissipated by the FET.…”

“…The 0018-9383/01$10.00 © 2001 IEEE total FET-drain current measured is therefore the sum of the bipolar-transistor collector-current , the impact ionization current , and the normal FET drain-current without-impact-ionization . The parasitic bipolar-transistor which introduces part of the low-frequency dispersions in SOI-MOS-FETs, performs with its long time response the seam-less integration between 1) the isothermal dc -characteristics (2) which sets the transistor's dc biasing and 2) the pulsedcharacteristics…”