I am designing a non-inverting op-amp circuit that maps an input signal (V3) 0-3.3V to an output signal (Vo) 0.2-2.4V. I opted to offset the output up by 0.2V and then used a second op-amp circuit as a negative impedance converter (NIC) to attenuate the 3.3V input to 2.4V at the output. The schematic can be seen below:
Simulating the circuit using the spice model for the LM258 gives roughly excellent results (as it always does) that I would be happy with:
In reality, when I prototype the circuit, the output hits 2.4V just fine at the high end, but cannot go below ~0.7V at the low end. When I disconnect the NIC and short circuit the inputs of X1 it works just fine at the low end (but of course the output goes beyond 2.4V at the high end). Can someone explain to me why the NIC is preventing the output from going as low as I want it to and how to overcome that?