Balanced bi-directional current source

The present invention relates to data storage systems and, more particularly, to a transfer curve tester having a bi-directional current source for testing magnetic recording heads used in data storage systems. A balanced bi-directional current source is provided, which includes first and second current output terminals, a current control circuit, first and second amplifiers and first and second sense impedances. The current control circuit has a reference input, a feedback input, and a control output, which is based on the reference input and the feedback input. The first amplifier has a first amplifier input, which is coupled to the control output, and a first amplified output. The second amplifier has a second amplifier input, which is coupled to the control output, and a second amplified output, which is inverted relative to the first amplified output. The first sense impedance is coupled in series between the first amplified output and the first current output terminal and has a feedback output which is coupled to the feedback input. The second sense impedance is matched with the first impedance and is coupled in series between the second amplified output and the second current output terminal.