ON THE INTRINSIC SHORT-CIRCUIT CURRENT GAIN OF DIFFUSED BASE TRANSISTORS.
Scientific rept. no. 11,
NEW YORK UNIV N Y LAB FOR ELECTROSCIENCE RESEARCH
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An analytic approximation to the expression for the intrinsic short-circuit current gain of the diffused base transistor in the common base configuration is obtained. The method of approximation utilizes the product expansion of the transcendental functions. The infinite product expansion shows the effects of all the poles of the gain function. The equations are simple to interpret and give insight into the operation of the transistor in the region above the alpha cutoff frequency. An analytic expression for the single pole approximation with excess phase is also obtained which method avoids tedious and involved computations made to determine the 3db frequency and the phase angle at the 3db frequency or a somewhat higher frequency. The analytic approximate expression for the excess phase and the alpha cut-off frequency can be used to determine accurately these quantities in a simple manner from the physics of the device and in the entire useful frequency range of the transistor. Author