I've been reading about input offset voltage, bias current, and current offset for a few days now and still can't get some things straight.
I'll summarize what I understand and then pose the questions below. Please correct me if I'm wrong, it's difficult to find confirmation for these ideas.
1) Input offset voltage - Caused by mismatch in the input terminals of the opamp and specifies the voltage across the terminals that must be applied in order to get an output voltage of zero.
2) Input bias current - caused by the finite input resistance of the opamp and results in an "error" voltage drop that depends on the input impedance seen from the opamp terminals.
3) Input offset current - caused by a mismatch between the input bias currents of the individual terminals (not sure what this results in).
My questions are the following:
1) Does the input offset voltage simply add a DC component to all supplied AC signals, or is it relevant only when you want an output voltage of 0? Would one get rid of this offset voltage by simply AC coupling the input signal by adding a capacitor (and a resistor to ground)?
2) Is the best way to minimize the bias current by adding compensation resistance on the opamp terminal(s), so that the same potential difference appears across both terminals and the common mode signal rejection begins to take effect? What about when the bias signals are not matched on each terminal (which is what the input offset current specifies)?
3) What effect does the input offset current have on the output signal? Does it also introduce an error into the "actual" incoming signal?
I am fairly new to analog design and I'm trying to design an amplifier circuit that amplifies signals in the mV range (to also give output signals in the mV range, so low gain). This signal is being fed to expensive equipment (much, much, much more expensive than the amplifier circuitry) and I don't want to damage this. At the same time, I can't introduce significant errors into the signals that give me an amplified signal that is not representative of the original signal. I also need to quantitatively account for these errors.