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We present a new low-frequency noise model of a GaInP-GaAs HBT and the associated extraction process from measurements. Specific measurements enable us to locate the two dominant low-frequency noise sources. Their spectral densities extraction as a function of the emitter bias current is then performed and a normalized scalable model is deduced. The cyclostationarity of the low-frequency noise sources is justified. The whole noise model including the shot noise source is implemented in the nonlinear HBT model used in the United Monolithic Semiconductors foundry. In order to verify the validity of the scalable noise model, several voltage-controlled oscillators with different center frequencies and tuning bandwidth have been designed and processed. Comparisons between the predicted performances and experimental results show an excellent agreement and validate the proposed low-frequency noise modeling of multifinger HBTs.

This paper presents a setup that enables wide-band (in-band and out-of-band) measurements of hot small-signal S-parameters of nonlinear devices driven by a large-signal single tone (namely, the pump signal). A load-pull characterization is performed at the pump frequency (F/sub 0/), while hot small-signal S-parameters are measured with a perturbating signal at a frequency (f) by the use of a probe tone. Basically, the frequency of the probe tone is swept over a wide bandwidth (at the present time from 300 MHz up to F/sub 0//2). A higher frequency range, from near dc to KF/sub 0/, will be implemented in a similar manner. The measurement setup reported here is applied to on-wafer measurements of S-band HBTs. Hot small-signal S-parameter measurements versus large-signal load impedance and pump level will be shown. An application to the prediction of parametric oscillations will be demonstrated. A parametric oscillation predicted at 373 MHz is confirmed by spectrum measurements.

For phase noise evaluation in feedback oscillators, the Leeson formula is a useful tool. Nevertheless, a direct application to oscillator circuits with complex feedback tanks can lead to erroneous results because the Leeson formula contains a coefficient, namely, "the loaded quality factor of the circuit," which is not the right coefficient to be used in the expression. It turns out that, in the Leeson formula, this latter coefficient coincides with the loaded Q-factor of the circuit only for specific elemental feedback tanks. We have derived the right coefficient in terms of the energy stored and power dissipated in the circuit. It may be shown that its expression is definitively different from that of the loaded Q-factor of the circuit. We obtain a modified Leeson formula valid for all feedback oscillator circuits. It should be noted that all the electrical models and calculations presented in this paper are valid for FETs as well as for bipolar transistors. A comparison with nonlinear simulations of the phase noise in oscillator circuits with complex feedback tanks demonstrates the validity of the new expression.

A novel approach for determining the amplitude and frequency of nonlinear FET oscillators is presented. The nonlinear elements of the active device are modeled by the Volterra series method. The frequency and amplitude of oscillation are then calculated by solving two algebraic equations. Experimental results obtained from a constructed oscillator confirm the validity of the theory, the discrepancy between measured and calculated frequency and amplitude values being less than 10%. >

In this paper, an efficient approach to the optimum design of power amplifier stages is described. The impedances presented to the FET are optimized independently of the topology chosen for their realization. They are then synthesized by the usual methods of Iinear circuits. The proposed method has been applied to the design of broad-band power FET amplifiers. The realizations have given a good correlation between the theoretical and experimental results. Moreover, the method is being used in the optimum design of power FET multipliers.