Transistor common-base circuit

The common-base circuit for an npn transistor (Fig. 9.19A) seems logical and simple, but its efficiency in amplification is not obvious and must be explained. The npn transistor in a common-emitter circuit (Fig. 9.19B) is a bit easier to understand as a current amplifier. There are four rules ... 

Figure 15.1 showed the "common base" type of transistor hookup, in which two circuits share the same base lead. That particular variation required two batteries, each attached with opposite polarities, and this is a disadvantage of the circuit. Other variations of the common base circuit only need one battery, but they are more complex in other ways. 

Figure 10. Top, three-dimensional view of an oxide-isolated bipolar transistor. (Reproduced with permission from reference 13. Copyright 1988 McGraw-Hill.) Bottom, schematic of a common base n-p-n transistor circuit. Abbreviations are defined as follows n-epi, n-type-doped epitaxial-grown silicon and p-CHAN-STOPy p-type channel stop.

Depiction of bipolar junction transistors (A) npn and (B) pnp, and their representation in common-base or grounded-base circuit diagrams (C) npn, and (D) pnp, with the signs for positive currents I and voltages V indicated. (E) Four-terminal "black box" representation of the common-base npn circuit. After applying a small voltage vE, one measures a small current iE on the left, and on the output side one measures an output voltage vc and an output current ic the base current iB is not measured, but inferred. 

Common-base, common-emitter, and common-collector circuits for a bipolar npn transistor (A, B, C, respectively), and the equivalent grounded-grid, grounded-cathode, and grounded-plate circuits for vacuum-tube triodes (A corresponds to A, B to B, and C to C). Adapted from Terman [5]. 

A, B) Equivalent circuits for an npn transistor (C) In common-base configuration and (D) in common-emitter configuration. See Table 9.5 for numerical values. 

Common base amplifier circuit using a pnp transistor. An equivalent circuit can be constructed using an npn transistor by reversing the above polarities. 

Consider now the circuit of Fig. 6.3, which shows a transistor, T3, in the common-base configuration. If you suspect that there is something wrong in this circuit and that it may be responsible for the wrong behaviour of the network to which it is connected, check first the voltage between B and ground. If such a voltage substantially differs from the nominal value... 

Many types of oscillator circuits have been used for bulk wave sensors. Guilbault (29) uses a commercial transistor oscillator. For work in the presence of liquids, Thompson (11) reported the design of a system based on the use of an automatic gain control amplifier, while Bruckenstein (12) has used an all-TTL digital logic oscillator design. The jigs and fixtures described in the work cited in this section are also quite typical of what is in common use. 

The transformer inductance plus the parallel capacitance is called a "tank circuit." It can be attached to any of the three transistor wires, but in this case (position C), it is being used on the collector, which is the most commonly used position. (If the inductor on the base has no capacitor, it is not a tank circuit.)... 

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