Characterizing BJTs using the Early voltage in the forward active mode

Summary Bipolar junction transistors (BJTs) have been at the core of linear electronics from its beginnings. Here, we suggest an Early‐based inspired geometric model of BJT devices and its application to derive models of related electronic circuits (more specifically a common‐emitter configuration)....

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Bibliographic Details
Published in:International journal of circuit theory and applications 2018-04, Vol.46 (4), p.978-986
Main Authors: Costa, Luciano da F., Silva, Filipi Nascimento, Comin, Cesar H.
Format: Article
Language:English
Subjects:
Angles (geometry)
Circuits
device model
early voltage
Electric potential
Electronic circuits
Emitters
Junction transistors
linearity
Mathematical models
parameter estimation
Semiconductor devices
Transfer functions
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Summary:Summary Bipolar junction transistors (BJTs) have been at the core of linear electronics from its beginnings. Here, we suggest an Early‐based inspired geometric model of BJT devices and its application to derive models of related electronic circuits (more specifically a common‐emitter configuration). The approach involves using a beam of isolines converging at the Early voltage as the model of a BJT. The angles of the isolines are experimentally verified often to vary almost linearly with the base current. A numerical methodology is suggested for the Early voltage estimation and applied to 12 real‐world small signal NPN BJTs. Interesting results are obtained, including the identification of diverse Early voltage values for different BJT types and estimation of transfer functions. A simple, yet effective, model of BJT is proposed based exclusively on the Early effect, and we show how important information, such as the device transfer function, can be respectively obtained. In addition, an experimental‐numeric procedure for estimating the Early voltage is described and probed, with good results on 12 BJTs. Figure (a) shows the estimation of the Early voltage, and Figure (b) illustrates the remarkable agreement between the experimental isolines and those obtained by the proposed model.
ISSN:0098-9886
1097-007X
DOI:10.1002/cta.2450