Impact of dynamic variability on the operation of CMOS inverter

The impact of dynamic variability due to low-frequency fluctuations on the operation of CMOS inverters, which constitute the basic component of SRAM cell, is investigated. The experimental methodology to characterise the effect of dynamic variability in a CMOS inverter is first established based on fast I-V measurements of the load current following the application of a ramp input voltage V_in(t). It is shown that, for small ramp rise times, the load current characteristics I_DD(V_in) exhibit a huge sweep-to-sweep dispersion due to low-frequency noise. The impact of such dynamic variability sources on the inverter´s output characteristics V_out(V_in) is finally demonstrated, revealing a 20% noise margin reduction for the smallest inverter cell.