Constant current regulator

Abstract

A constant current regulator includes a first transistor having a first terminal coupled with an input voltage; a second transistor having a first terminal coupled with a control terminal of the first transistor; a third transistor having a first terminal coupled with the first terminal of the first transistor and having a control terminal coupled with the first terminal of the second transistor; a first resistor having a first terminal coupled with a second terminal of the third transistor and having a second terminal coupled with a control terminal of the second transistor; a second resistor having a first terminal coupled with the control terminal of the second transistor and having a second terminal coupled with a second terminal of the second transistor; and a third resistor having a first terminal coupled with the second terminal of the third transistor and having a second terminal coupled with a fixed-voltage terminal.

What is claimed is: 
     
         1 . A constant current regulator ( 151 ), comprising:
 a first transistor ( 211 ), wherein a first terminal of the first transistor ( 211 ) is coupled with an input voltage (V 1 );   a second transistor ( 212 ), wherein a first terminal of the second transistor ( 212 ) is coupled with a second terminal and a control terminal of the first transistor ( 211 );   a third transistor ( 213 ), wherein a first terminal of the third transistor ( 213 ) is coupled with the first terminal of the first transistor ( 211 ), and a control terminal of the third transistor ( 213 ) is coupled with the first terminal of the second transistor ( 212 );   a first resistor ( 214 ), wherein a first terminal of the first resistor ( 214 ) is coupled with a second terminal of the third transistor ( 213 ), and a second terminal of the first resistor ( 214 ) is coupled with a control terminal of the second transistor ( 212 );   a second resistor ( 215 ), wherein a first terminal of the second resistor ( 215 ) is coupled with the control terminal of the second transistor ( 212 ), and a second terminal of the second resistor ( 215 ) is coupled with a second terminal of the second transistor ( 212 ); and   a third resistor ( 216 ), wherein a first terminal of the third resistor ( 216 ) is coupled with the second terminal of the third transistor ( 213 ), and a second terminal of the third resistor ( 216 ) is coupled with a fixed-voltage terminal.   
     
     
         2 . The constant current regulator ( 151 ) of  claim 1 , wherein the first transistor ( 211 ) is a metal-semiconductor field effect transistor.