Cut-off frequency of a drift transistor
About: This article is published in Solid-state Electronics.The article was published on 1967-04-01. It has received 7 citations till now. The article focuses on the topics: Static induction transistor & Threshold voltage.
Citations
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01 Jan 1980
TL;DR: In this article, the energy diagram for an npn transistor without bias is given in Fig. 4.1(a), with forward bias on the emitter-base junction, electrons are injected into the base and by diffusion make their way to the base-collector region which is reverse-biased so that the electric field in the depletion region aids the collection.
Abstract: Bipolar transistors are npn or pnp structures where the current flow across the base region is by minority carriers injected from an emitter region. This minority carrier flow is collected at a reverse-biased collector junction. The energy diagram for an npn transistor without bias is given in Fig. 4.1(a). With forward bias on the emitter-base junction, electrons are injected into the base and by diffusion make their way to the base-collector region which is reverse-biased so that the electric field in the depletion region aids the collection, as in Fig. 4.1(b). If the base region is graded in doping, as in Fig. 4.1(c), the transport of electrons across the base is aided by the electric field there and the frequency response of the transistor is increased.
TL;DR: In this paper, the Kroemer equation giving the base transport factor in single-diffused transistors (constant aiding field in the base) is extended to cover double-differentiated transistors, and the base retarding held is found to have an important degradation effect on the cut-off frequencies.
Abstract: Design graphs are developed for the intrinsic alpha cut-off frequencies ωα, and ωT, and for the excess phase m of bipolar transistors. The Kroemer equation giving the base transport factor in single-diffused transistors (constant aiding field in the base) is extended to cover double-diffused transistors (constant aiding and retarding fields in the base). The base retarding held is found to have an important degradation effect on the cut-off frequencies: a 2 kT/q retarding voltage extended along 20% of the base width diminishes ωα,to about half the value corresponding to a single-diffused transistor. A practical design criterion is given for optimizing the impurity-concentration profiles of double-diffused transistors.
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TL;DR: In this paper, the authors used the theory of the simple one-dimensional model to find the frequency variation of the current gain of a drift transistor, and used this to find how junction capacitances and base resistance affect the measurement of the characteristic frequencies.
Abstract: Certain conventionally defined characteristic frequencies of a drift transistor are related to each other, to the basic transistor parameters, and to minority carrier time constants, using the theory of the simple one-dimensional model The Frequencies are the common emitter and common base cut-off frequencies, and the frequency at which the magnitude of the common emitter short circuit current gain is unity; the minority carrier time constants are the effective lifetime, the average transit time, and the average time of stay in the base Several approximations for the frequency variation of the current gains are given, and used to find how junction capacitances and base resistance affect the measurement of the characteristic frequencies Finally the maximum frequency of oscillation is discussed, and the high-frequency figure of merit redefined in a way compatible with the conventional definition
9 citations