The charge-based equations in [1] give

                  (1)

where

  (2)

is the value of the transconductance-to-current ratio deep in weak inversion.

In the ACM model the threshold voltage (V_T) is defined as the value of V_G for which the drift and diffusion components of the drain current are equal (q'_I = 1). Applying this criterion to (1) for small V_DS (q'_IS approximately equal to q'_ID) and assuming n (slope factor) to be almost constant, allows the extraction of the threshold voltage from the g_m/I_D characteristic (Fig.1) by simply measuring the peak value of g_m/I_D and determining the gate voltage at which the value of g_m/I_D drops to one-half of the peak value. Applying the previously described methodology to the curve generated using the PSP model in ELDO, we find V_TO=208 mV and I_SQ=158 nA. To generate the transconductance-to-current ratio in Fig. 1 associated with the ACM model we embedded the values of V_TO=208 mV andI_SQ=158 nA. The Fig.1 shows that the PSP and ACM fits very well and the transconductance-to-current characteristic should be used to determined V_TO and I_SQ.

Fig.1 Transconductance-to-current characteristic of an n-MOS transistor for V_DS=1mV. The PSP curve was used to determine both the threshold voltage and the sheet specific current.

INTRODUCTION