Microwave and Wireless Communications Technology

244 MICROWAVE TRANSISTORS

5. The stability

of transistor amplifiers refers to freedom from spurious oscil-

lations. Three basic conditions are recognized:

unstable

(oscillating),

unconditionally

stable,

and

conditionally stable. The

criteria for these conditions depend in part on the

nature of the circuit impedances.

6. Three basic geometries contribute to improved microwave performance

of bipolar transistors:

interdigited, matrix,

and

overlay.

7. Three main contributors to the overall bipolar device noise figure are

thermal noise, emitter-to-base shot noise,

and

collector-to-base shot noise.

Thermal noise

can be reduced both ...