I am having trouble summing 3 signals. I am trying to sum the 455kHz IF frequencies from 3 separate Phillips SA612 mixer/oscillator chips. I have simulated it in Multisim, but the real world results are not even close. I am using a TLC2272 for an op-amp in a non-inverting configuration. My experience in this arena is limited, apparently I have something to learn about op-amps. Thanks in advance.