A circuit and method for level-shifting an input signal are disclosed that
provide for level-shifting of a the input signal where an external voltage
level is greater than an internal voltage of the signal. In the present
invention, the input signal is compared to a reference signal to produce a
differential current signal reflecting the logic level of the input
signal. The differential current signal is reflected through a pair of
current mirrors operating from the external voltage level to drive a pair
of resistive loads. Each of the resistive loads is coupled in series with
a current sink between the internal supply voltage and a ground voltage.
As a result, the input signal may be received and level-shifted with gain
even when the internal supply voltage is less than twice a transistor
threshold voltage without introducing significant distortion to the
received signal.
