2-28 and is related to collector-to-base current gain, beta (b), of the common-emitter circuit by the formula: Since a given transistor may be connected in any of three basic configurations, there is a definite relationship, as pointed out earlier, between alpha (a), beta (b), and gamma (g). These relationships are listed again for your convenience: Take, for example, a transistor that is listed on a manufacturer's data sheet as having an alpha of 0.90. We wish to use it in a common emitter configuration. This means we must find beta. The calculations are: Therefore, a change in base current in this transistor will produce a change in collector current that will be 9 times as large. If we wish to use this same transistor in a common collector, we can find gamma (g) by: To summarize the properties of the three transistor configurations, a comparison chart is provided in table 2-1 for your convenience. Table 2-1.—Transistor Configuration Comparison Chart AMPLIFIERTYPE COMMON BASE COMMON EMITTER COMMON COLLECTOR INPUT/OUTPUT PHASE RELATIONSHIP 0º 180º 0º VOLTAGE GAIN HIGH MEDIUM LOW CURRENT GAIN LOW(!) MEDIUM(") HIGH(#) POWER GAIN LOW HIGH MEDIUM INPUT RESISTANCELOW MEDIUM HIGH OUTPUT RESISTANCEHIGH MEDIUM LOW