Predictions based on the maximum oscillator frequency of a transistor

A vertical silicon-graphene-germanium transistor

“…For a BJT, a main figure of merit is the alpha cutoff frequency f α , which is used to represent the upper frequency limit when a BJT is biased in the common base mode. f α is inversely proportional to the delay time, which includes the emitter charging time τ e , the base transit time τ b , and the collector delay time τ c 2–5 . In the past decades, there has been a persistent demand for higher frequency operation for a BJT, leading to the inventions of new devices, such as heterojunction bipolar transistors and hot electron transistors.…”

Frequency Domain Stability Criteria for Large-Signal Tuned Common-Base Amplifiers

“…First, because the superposition viewpoint lacks rigorous mathematical justification, the definition of the class A and 'nonlinear components is somewhat arbitrary. Accordingly, the degree to which spurious frequencies are induced by such linear phenoinena as intrinsic device feedback [5], [6], and parasitic thermal effects [7], [8], and by such nonlinear phenomena as avalanche [9], [ [20] and in general, the derived stability conditions are predicated on overly restrictive approximations.…”

Conjugate-image operation of transistor amplifiers

“…This can be done by externally feeding back a signal of equal magnitude and opposite phase to that fed back internally. Gade (15) Drouilhet (12) considers the prediction of transistor amplifier per formance based on the maximum frequency of oscillation of the transistor.…”