Current sense amplifier

A current sense amplifier, which comprises a preamplifier having 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 obtaining a preamplifier positive output at a positive output end and obtaining a preamplifier negative output at a negative output end in accordance with a difference between the upper voltage and the lower voltage, wherein

• the preamplifier comprises an input gain section to which the upper voltage and the lower voltage are input and which obtains an input gain section negative output and an input gain section positive output based on a difference between them,
• the input gain section positive output and the input gain section negative output are connected to a positive power supply via the respective ones of two p-channel transistors,
• the gates of the two p-channel transistors are connected to each other, and are further connected to the preamplifier negative output and the preamplifier positive output via two pull-up resistors, respectively,
• the input gain section positive output and the input gain section negative output are connected to the gates of n-channel transistors, respectively,
• the sources of the respective n-channel transistors are connected to the preamplifier negative output and the preamplifier positive output, respectively, and
• the n-channel transistors are native-type transistors or depletion-type transistors whose gate-source voltage when active is relatively small.

A current sense amplifier, which comprises a preamplifier having 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 obtaining a preamplifier positive output at a positive output end and obtaining a preamplifier negative output at a negative output end in accordance with a difference between the upper voltage and the lower voltage, wherein

• the preamplifier
• comprises an input gain section to which the upper voltage and the lower voltage are input and which obtains an input gain section negative output and an input gain section positive output based on a difference between them,
• the input gain section positive output and the input gain section negative output are connected to a positive power supply via the respective ones of two p-channel transistors,
• the gates of the two p-channel transistors are connected to each other, and are further connected to a preamplifier negative output and a preamplifier positive output via two pull-up resistors, respectively,
• the input gain section positive output and the input gain section negative output are connected to the gates of p-channel source follower transistors, respectively,
• the sources of the respective p-channel source follower transistors are connected to the preamplifier negative output and the preamplifier positive output, respectively, and
• the respective p-channel source follower transistors receive a constant current from a constant current source to operate.