BJTl

BJTl is a term used in some sources to denote a lateral bipolar junction transistor, a configuration in which the emitter and collector regions extend laterally on a semiconductor substrate rather than penetrating vertically through a layered structure. In a BJTl, the base is a planar region between the two diffused emitter and collector regions, and the device is typically fabricated in planar process technologies that are common in integrated circuits.

Like other BJTs, a BJTl operates by forward biasing the emitter-base junction to inject carriers into the base, where they are swept into the collector by the reverse-biased base-collector junction. The current gain, or beta, depends on device geometry, doping, and manufacturing process, and in lateral devices it is often lower than in modern vertical BJTs. The small-signal model uses standard transistor parameters such as r_pi and g_m, and the frequency response is influenced by carrier transit times and diffusion lengths in the lateral structure.

Compared with vertical BJTs, BJTl devices typically offer easier integration with planar IC processes and simpler isolation in certain process flows, but they may exhibit higher on-resistance and lower breakdown voltages due to their geometry. They can be found in older or specialized integrated circuits and in some discrete transistor applications where planar geometry is advantageous. In contemporary literature, the term BJTl is sometimes used interchangeably with lateral BJT, though terminology varies by vendor and historical context.