High-efficiency energy-saving current amplifier

The invention provides a high-efficiency energy-saving current amplifier, belongs to the field of relay protection test apparatuses, and in particular relates to a relay protection tester. A drain D of an NMOS tube, which is taken as an input end, is connected with an output end of a current amplifier equivalent module; a source of the NMOS tube, which is taken as an output end, is connected with a load; a grid of the NMOS tube is connected with a logic control loop; the value of a sampling resistor R15 is reduced from 0.1 ohm to 0.02 ohm; an added sampling resistor R16 with the value of 0.3 ohm is added between the drain D and the source S; on and off of the NMOS tube are controlled through the voltage size of the grid; when output current of the current amplifier is larger than or equal to 15 A, the voltage of the grid is up to a threshold; when the NMOS tube is in an on state, current flows through a branch of the NMOS tube; when the output current of the current amplifier is smaller than 15 A, the voltage of the grid is not up to the threshold, the NMOS tube is in an off state, and the current flows through a branch of the added sampling resistor. According to the high-efficiency energy-saving current amplifier, which is provided by the invention, when the voltage of the grid is up to the threshold, the NMOS tube has the capability of forming a conducting channel between the source and the drain; therefore, the power loss of the relay protection tester current amplifier is reduced, the sampling precision is improved, the investment is reduced, the maximum output current is increased and the like.