A low voltage regulated current source includes a feedback amplifier that forces a node voltage in both branches of the current mirror to equal to each other, by adjusting voltages in two branches of the current mirror to be equal to each other. The low voltage current mirror also has a higher output impedance compared to other current mirrors.
Description
BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES
The present invention is described with reference to the accompanying drawings.
FIGS. 1-3 illustrate circuit diagrams of known current mirrors;
FIG. 4 illustrates a circuit diagram of a current mirror according to an embodiment of the present invention.
FIG. 5 illustrates a circuit diagram of a current mirror according to another embodiment of the present invention.
Claims
1. A current mirror circuit comprising:
a reference current side configured to generate a reference current, the reference current side having a plurality of transistors;a load current side configured to generate a load current proportional to the reference current, the load current side having a first transistor coupled to a second transistor of the plurality of transistors of the reference current side; anda feedback circuit configured to provide a voltage difference between a terminal of the first transistor of the load current side and a terminal of the second transistor to a terminal of a third transistor of the plurality of transistors.
2. The current mirror circuit of claim 1, wherein the feedback circuit is an amplifier.
3. The current mirror circuit of claim 2, wherein the amplifier has a first input, a second input, and an output, the first input is coupled to the terminal of the first transistor of the load current side, the second input is coupled to the terminal of the second transistor of the reference current side, the output is coupled to the terminal of the third transistor of the reference current side.
4. The current mirror circuit of claim 3, wherein the first input is a non-inverting input and the second input is an inverting input.
5. The current mirror circuit of claim 1, wherein the terminal of the first transistor and the terminal of the second transistor are drain terminals.
6. The current mirror circuit of claim 1, wherein a gate terminal of the first transistor of the load current side is coupled to a gate terminal of the second transistor of the reference current side.
7. The current mirror circuit of claim 1, wherein the terminal of the third transistor is a gate terminal.
8. The current mirror circuit of claim 1, wherein a drain terminal of the third transistor is coupled to the gate terminal of the second transistor.
9. A current source comprising:
a first transistor have a first and second terminals;a second transistor coupled to the second terminal of the first transistor;a third transistor having a third and a fourth terminal, the third terminal coupled to the second transistor, the fourth terminal coupled to a load circuit; anda circuit outputting a voltage difference between the second terminal and the fourth terminal to the first terminal.
10. The current source of claim 9, wherein the circuit is an amplifier.
11. The current source of claim 10, wherein the amplifier has a first input, a second input, and an output, the first input is coupled to the fourth terminal, the second input is coupled to the second terminal, the output is coupled to the first terminal.
12. The current source of claim 11, wherein the first input is a non-inverting input and the second input is an inverting input.
13. The current source of claim 1, wherein the second node is a drain node and the second terminal is a source terminal.
14. The current source of claim 1, wherein a gate terminal of the second transistor is coupled to a gate terminal of the third transistor.
15. The current source of claim 1, wherein the first terminal is a gate terminal.
16. The current source of claim 1, wherein a drain terminal of the first transistor is coupled to the gate terminal of the second transistor.
Patent Application
20070229150
