Current sense amplifier

A current sense amplifier, comprising:

• a preamplifier that has a preamplifier positive input end to which an upper voltage of a current detection resistor is input and a preamplifier negative input end to which a lower voltage of the current detection resistor is input, and obtains a preamplifier positive output at a positive output end and obtains a preamplifier negative output at a negative output end in accordance with a difference between the upper voltage and the lower voltage;
• and
• a post-amplifier that has a post-amplifier negative input end to which the preamplifier negative output is input and a post-amplifier positive input end to which the preamplifier positive output is input, and obtains a post-amplifier output corresponding to a difference between the preamplifier positive output and the preamplifier negative output;
• wherein
• the post-amplifier comprises:
• a second operational amplifier in which the preamplifier negative output is input to a second operational amplifier negative input end, the preamplifier positive output is input to a second operational amplifier positive input end, and a second operational amplifier output is obtained based on a difference between them;
• a second operational amplifier positive side input resistor disposed in an input path to the second operational amplifier positive input end;
• a second operational amplifier negative side input resistor disposed in an input path to the second operational amplifier negative input end;
• a second operational amplifier feedback resistor disposed in a feedback path from a second operational amplifier output end to the second operational amplifier negative input end;
• and
• a resistor network which connects the second operational amplifier positive input end to a reference power supply and a ground, and in which a combined resistance value from the second operational amplifier positive input end to the reference power supply and the ground corresponds to the resistance value of the second operational amplifier feedback resistor.