Which term describes the error voltage associated with input bias currents?

Which term describes the error voltage associated with input bias currents?

• A. Input bias current
• B. Output offset voltage
• C. Common mode error
• D. Voltage gain

Answer: (B)

Bias currents flowing into the op-amp inputs must pass through the resistances connected to those inputs. This creates small voltage drops that appear as a DC error at the input node. Because the amplifier’s feedback tries to keep the inputs at the same potential, those input-referenced errors get carried through the circuit and show up as a DC offset at the output. The term used for this DC error observed at the output, caused by the input bias currents, is the output offset voltage. The other terms don’t describe this specific effect: the input bias current is the actual current into the inputs, not the resulting voltage error; common mode error relates to how the circuit handles signals common to both inputs rather than to bias-current–induced offset; and voltage gain is the amplification factor, not an offset voltage.

Bias currents flowing into the op-amp inputs must pass through the resistances connected to those inputs. This creates small voltage drops that appear as a DC error at the input node. Because the amplifier’s feedback tries to keep the inputs at the same potential, those input-referenced errors get carried through the circuit and show up as a DC offset at the output. The term used for this DC error observed at the output, caused by the input bias currents, is the output offset voltage.

The other terms don’t describe this specific effect: the input bias current is the actual current into the inputs, not the resulting voltage error; common mode error relates to how the circuit handles signals common to both inputs rather than to bias-current–induced offset; and voltage gain is the amplification factor, not an offset voltage.