Hi, I'm using an emitter follower op-amp buffer with LM6132 and PN2222A. I'm expecting almost an exact follow?, as simulated with multisim. However, I'm getting an output offset of around 50mV at zero input. Reading LM6132 I should be able to swing to 0 with +/-5v supply. I'm wondering if it's an op amp input offset problem, I'll be testing this when I have access to an oscilloscope. Also, I'm using a DC-DC converter for my two rails, specifically 102-3333-1-ND, and I have yet to add input/output capacitors to the converter.
The emitter follower can only source current, it cannot sink it*. The LM6132 has an input bias current of (typically) 110nA at room temperature. That current flows out of the op-amp input.
If you connect it to a 500K load to ground, you'll get around 50mV of output offset. To make this go away you could add an E-B resistor- something like 1K should work very well.
*If you had a -10V supply it would probably appear to work since the transistor E-B junction would break down. This is not a good thing. Even with your +/-5V supplies it would be a good idea to add a reverse-biased diode such as a 1N4148 across the E-B junction (in parallel with the resistor I mentioned above).