Empirical expression for base transit time in bipolar transistors

Khan, Md. Ziaur Rahman; Hassan, Muhammad; Rahman, Talha; Ahsan, A.K.M.

doi:10.1080/00207210500095902

Cited by 3 publications

References 5 publications

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A New Technique for Determining Base Transit Time of a Bipolar Junction Transistor

Nomani

Hassan

2006

2006 International Conference on Electrical and Computer Engineering

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A base transit time model for an npn bipolar junction transistor with exponential-doped base at high level of injection, which is applicable for all levels of injection before the onset of the Kirk effect, is developed. Based on the realistic assumption that a small change in electron concentration in the base at high injection occurs from its modified low injection model incorporating Webster effect, mathematical expressions for minority carrier concentration and current density have been derived. In this work, electric field dependence of mobility in addition to doping dependent mobility, bandgap-narrowing effect, high-injection effect and carrier velocity saturation at the base edge of the base-collector junction are incorporated. The base transit time is found to be different if the field dependent mobility is considered. The analytically calculated base transit time is found to be in good agreement with numerical results available in literature.

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A New Technique for Determining Base Transit Time of a Bipolar Junction Transistor

Nomani

Hassan

2006

2006 International Conference on Electrical and Computer Engineering

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Base transit time of a bipolar junction transistor considering majority-carrier current

Chowdhury

Hassan

2008

2008 International Conference on Electrical and Computer Engineering

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In this paper an analytical expression for base transit time τ B for an npn bipolar transistor considering majoritycarrier current density is obtained. For finding τ B , expressions for minority-carrier electron current density J n, majority-carrier hole current density J p and electron concentration, n(x) are analytically derived. In the model energy-bandgap-narrowing effects due to heavy doping, velocity saturation as well as doping and field dependent mobility are considered. It is found that, in the low-injection condition, τ B depends on Jp and its value is found greater than the value if J p is neglected. In finding τ B , previous works neglected Jp. The closed-form analytical expressions offer a clear physical insight into device operations at various bias conditions.

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Base-transit-time model considering field dependent mobility for BJTs operating at high-level injection

Hassan

Nomani

2006

IEEE Trans. Electron Devices

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Empirical expression for base transit time in bipolar transistors

Cited by 3 publications

References 5 publications

A New Technique for Determining Base Transit Time of a Bipolar Junction Transistor

A New Technique for Determining Base Transit Time of a Bipolar Junction Transistor

Base transit time of a bipolar junction transistor considering majority-carrier current

Base-transit-time model considering field dependent mobility for BJTs operating at high-level injection

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