7.3.1 Input Stage

The LMV7235 and LMV7239 are rail-to-rail input and output. The typical input common-mode voltage range of −0.2 V below the ground to 0.2 V above the supply. The LMV7235 and LMV7239 use a complimentary PNP and NPN input stage in which the PNP stage senses common-mode voltage near V⁻ and the NPN stage senses common-mode voltage near V⁺. If either of the input signals falls below the negative common mode limit, the parasitic PN junction formed by the substrate and the base of the PNP will turn on resulting in an increase of input bias current.

If one of the inputs goes above the positive common mode limit, the output will still maintain the correct logic level as long as the other input stays within the common mode range. However, the propagation delay will increase. When both inputs are outside the common-mode voltage range, current saturation occurs in the input stage, and the output becomes unpredictable.

The propagation delay does not increase significantly with large differential input voltages. However, large differential voltages greater than the supply voltage should be avoided to prevent damage to the input stage.