CD40109B contains four low-to-high-voltage level-shifting circuits. Each circuit will shift a low-voltage digital-logic input signal (A, B, C, D) with logical 1 = V_CC and logical 0 = V_SS to a high-voltage output signal (E, F, G, H) with logical 1 = V_DD and logical 0 = V_SS.

The RCA-CD40109, unlike other low-to-high level-shifting circuits, does not require the presence of the high-voltage supply (V_DD) before the application of either the low-voltage supply (V_CC) or the input signals. There are no restrictions on the sequence of application of V_DD, V_CC, or the input signals. In addition, with one exception there are no restrictions on the relative magnitudes of the supply voltages or input signals within the device maximum ratings, provided that the input signal swings between V_SS and at least 0.