Patent ID: 7495470

Claim:
A negative feedback circuit, comprising: a reference resistor ( 302 ) having a first end and a second end, the second end of the reference resistor ( 302 ) being connected to a common end; a first variable resistor ( 304 ) having a first end, a second end and a third regulating end, the second end of the first variable resistor ( 304 ) being connected to the common end; a second variable resistor ( 306 ) having a first end, a second end and a third regulating end; a voltage follower ( 308 ) having a first end, a second end and a third end, the first end of the voltage follower ( 308 ) being connected to the first end of the reference resistor ( 302 ) at node A; the voltage follower ( 308 ) being configured to make voltage at node A, VA, follow a reference voltage inputted to the third end of the voltage follower ( 308 ); a proportional current mirror ( 310 ) having an input end and an output end; the input end of the proportional current mirror ( 310 ) being connected to the second end of the voltage follower ( 308 ) and the output end of the proportional current mirror ( 310 ) being connected to the first end of the first variable resistor ( 304 ) at node B; the proportional current mirror ( 310 ) being configured to output a current of the output end of the proportional current mirror ( 310 ) in proportion to a current of the input end of the proportional current mirror ( 310 ); the current of the input end being a reference current via the reference resistor; and a comparison arbiter ( 312 ) having a first input end, a second input end, a first output end and a second output end, node A and node B being connected to a first input end and a second input end of the comparison arbiter ( 312 ), respectively; the comparison arbiter ( 312 ) being configured to compare the voltage at node A and the voltage at node B to acquire a regulating signal; the regulating signal being used for synchronously regulating the resistances of the first variable resistor ( 304 ) and the second variable resistor ( 306 ) so as to make the voltage at node B approach to the voltage at node A.