The pH variation was used to detect the concentration of urea. E-mail: Ībstract: In this study, a urea biosensor was prepared by the immobilization of urease onto the sensitive membrane of an extended-base bipolar junction transistor. This link is the main feature of transistor action.Issue title: Frontiers in Biomedical Engineering and Biotechnology – Proceedings of the 2nd International Conference on Biomedical Engineering and Biotechnology, 11–13 October 2013, Wuhan, ChinaĪuthors: Sun, Tai-Ping | Shieh, Hsiu-Li | Liu, Chun-Lin | Chen, Chung-Yuan Īffiliations: Institute of Electrical Engineering, National Chi Nan University, Nantou, 545, Taiwan, ROC | Graduate Program of Optoelectronic Technology, National Chi Nan University, Nantou, 545, Taiwan, ROC Therefore if a transistor has a Beta value of 50, then for every 50 electrons flowing between the emitter-collector terminals one electron will flow from the base terminal.īy combining the expressions for both Alpha, α and Beta, β the current gain of the transistor can be given as:Īs seen from the equations above, electron mobility between the Collector and Emitter circuits is the only link between these two circuits. Beta values normally range between 20 and 200 for most general purpose transistors. NPN transistors are good amplifying devices when the Beta value is large. The current gain of the transistor from the Collector terminal to the Base terminal is signified by Beta, ( β ). The current gain of the transistor from the Collector terminal to the Emitter terminal, Ic/Ie, is a function of the electrons diffusing across the junction. The ratio of the collector current to the emitter current is called Alpha (α). Since the physical construction of the transistor determines the electrical relationship between these three currents, (Ib), (Ic) and (Ie), any small change in the base current ( Ib ), will result in a much larger change in the collector current ( Ic ). Note: “Ic” is the current flowing into the collector terminal, “Ib” is the current flowing into the base terminal and “Ie” is the current flowing out of the emitter terminal.
The current flowing out of the transistor must be equal to the currents flowing into the transistor as the emitter current is given as A nother way to display a NPN Transistor is shown in Figure 2 below. The Base terminal is always positive with respect to the Emitter. The voltage between the Base and Emitter ( V BE ), is positive at the Base and negative at the Emitter.
\): NPN Transistor schematic.įor a bipolar NPN transistor to conduct the Collector is always more positive with respect to both the Base and the Emitter.
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