Millimeter-wave AlGaAs-GaAs HBT power operation
The AlGaAs-GaAs HBT has demonstrated good power performance up to 18 GHz. Although f/sub max/ is typically above 100 GHz, the power performance limitation and large signal operation at millimeter wave frequencies have not been studied. Power results from two HBT structures at 35 GHz are analyzed based on numerical simulation. The HBT demonstrated 8.5-dB linear power gain, 30% PAE with 7.8-dB gain and 7.5-V V/sub ce/ bias. The power density reaches 1.25 mW/ mu m/sup 2/. A shorter collector (0.4 mu m) is shown to be better suited for 35-GHz operation as a result of shorter collector transit time and smaller residual collector voltage. Improvement can be achieved by reducing the base and collector resistance, and the collector capacitance.<<ETX>>
Design considerations for millimeter-wave power HBTs based on gain performance analysis
Critical design issues involved in optimizing millimeter-wave power HBTs are described. Gain analysis of common-emitter (CE) and common-base (CB) HBTs is performed using analytical formulas derived based on a practical HBT model. While CB HBT's have superior maximum-gain at very high frequencies, their frequency limit is found to be determined by the carrier transit time delay. Thus, to fully exploit the potential gain in a CB HBT, it is essential to maintain a high f/sub T/ even at high collector voltages. The advantage of using CB HBT's in a multifingered device geometry is also discussed. Unlike CE HBTs, CB HBTs are capable of maintaining a high gain even if the device size is scaled up by increasing the number of emitter-fingers. Moreover, it is found that reducing the wire parasitic capacitance allows emitter ballasting resistance to be used without affecting the gain. Fabrication of HBTs based on these design considerations led to excellent power performance in a CB unit-cell HBT at 25-26 GHz, featuring output power of 740 mW and power-added efficiency of 42%.
Nurse responsiveness to cancer patient expressions of emotion.
OBJECTIVE
This theoretically based study examined nurse responses to cancer patient expressions of emotion using a videotaped, simulated cancer patient.


METHODS
This study used an experimental crossover design with a videotaped patient expressing anger, sadness, and neutral emotion to elicit nurse responses. Seventy-four nurses from eight sites participated. Responses were coded using Roter interaction analysis system. Correlations explored relationships between variables that impact communication (age, gender, work experience, trait anxiety, work stress, self-efficacy). Regression models explored the effect of variables on nurse affective responsiveness.


RESULTS
Patient expressions of sadness elicited more affective responses than anger. Expressions of anger or neutral emotion elicited more instrumental behaviors than sadness. Variables such as age, work stress and work experience were significantly correlated. No variables predicted affective responsiveness to patient expressions of anger or sadness.


CONCLUSION
Nurse communication showed significant variation in response to patient emotional expressions. Understanding the relationships between demographic, personality, and work variables, and identification of new variables that influence nurse-patient communication, has implications for interventional studies.


PRACTICE IMPLICATIONS
Over 90% of the participants indicated that the videotape simulation would be a useful method for teaching and practicing communication skills with patients expressing emotions.