Common Base Amplifier

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

If a load is placed in series with the source providing the reverse bias to the collector circuit, the voltage across the load is 

Let Rl = 5 KO, Ie = 5 mA, kTje = 0.026 V, a 1, the voltage gain is 1000. In this case the voltage gain is determined by the load resistor and can be virtually any value. 

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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 7.23 Common chemically amplified resist platforms based on poly (hydroxystyrene) and used in DUV lithographic applications. (Courtesy of R. Dammel.)...

The BJT is a three electrode or triode electron device. When connected in a circuit it is usually operated as a two-port, or two-terminal, pair device as shown in Fig. 7.8. Therefore, one of the three electrodes of the BJT must be common to both the input and output ports. Thus, there are three basic BJT configurations, common emitter (CE), common base (CB), and common collector (CC), as shown in Fig. 7.8. The most often used configuration, especially for amplifiers, is the common-emitter (CE), although the other two configurations are used in some apphcations. 

Many detectors have been developed to collect and amplify the primary ionization created by nuclear particles. In principle, the careful measurement of this ionization provides the most information about the particle and its energy. The devices with the highest resolution are these detectors based upon ionization. Broadly speaking, ionization-based detectors have the common feature that the incident radiation creates ion pahs in an active volume of the device. An electric field is applied to the active volume to separate the charge pairs and sweep the ions to the electrodes. 

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