Boltzmann Law 
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Lab ActivitiesWhen Boltzmann's Law is applied to the motion of electrons in an npn transistor, it can be shown that the collector current is given by the equation I_{c} = I_{o} exp[(q V_{BE})/(K_{B} T)] where I_{o} = A(T) exp [( f/(K_{B} T)] In the second equiation, A(T) is a slowly varying function of temperature and f is the height of the barrier in the absence of an applied voltage. In the lab, students test the validity of the first equation by measuring Ic as a function of VBE in an npn transistor at three different temperatures (room temperature, in a dry icealcohol mixture and in mineral oil heated to ~91û C). For each temperature, graphs of log(Ic) as a function of VBE are made and the value of the ratio q/kB is computed from the slope of the plotted data. Next, the height of the barrier in electron volts, f/q , is computed from a plot of ln[IoT3/2] vs. 1/T . Finally, students are asked to estimate the validity of the assumption that A(T) µ T3/2 based on their data. Course LevelIntermediate: P49 Student Handouts
Equipment
Circuit Diagram
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