Three terminal measurements of current amplification factors of controlled rectifiers

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
\alpha_{n0}
and
\alpha_{p0}
of the n-p-n and p-n-p transistor sections constituting the Controlled Rectifier can be separately determined, together with f
n
and f
p
, 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
n
and α
P
. Measurements indicate that switching from high to low impedance is controlled by
\alpha_{n0} + \alpha_{p0} = 1
and not
\alpha_{n} + \alpha_{p} = 1
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.
\alpha_{n0}
and
\alpha_{p0}
were also measured and plotted as a function of voltage bias.