Three terminal measurements of current amplification factors of controlled rectifiers

Abstract

By treating the Silicon Controlled Rectifier as a hook transistor and measuring its current amplification factor as a function of frequency, the small-signal low-frequency alphas <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\alpha_{n0}</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\alpha_{p0}</tex> of the n-p-n and p-n-p transistor sections constituting the Controlled Rectifier can be separately determined, together with f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</inf> and f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> , their respective cutoff frequencies. Repeating these measurements at a number of bias currents, coupled with a numerical integration, enables one to separate the component dc currents of the two transistor sections as well as their dc alphas α <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</inf> and α <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</inf> . Measurements indicate that switching from high to low impedance is controlled by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\alpha_{n0} + \alpha_{p0} = 1</tex> and not <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\alpha_{n} + \alpha_{p} = 1</tex> as has hitherto been implied. There are good theoretical reasons for this which have led to a redefinition of the breakover conditions. These are shown to be given by infinite output admittance and not infinite current as has so far been thought to be the case. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\alpha_{n0}</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\alpha_{p0}</tex> were also measured and plotted as a function of voltage bias.