Power supply circuit for producing a reference current with a prescribable temperature dependence
View Patent ↗A power supply circuit is provided for producing a reference current with a prescribable temperature dependence. The circuit includes two current sinks, which at their respective input take up a first input current (I 1 ) or a second input current (I 2 ), and in which current sinks at their respective outputs are connected to a node having a reference potential, the output of at least one current sink being connected via a resistor to the node having the reference potential. The resistor is formed by least two reference resistors with prescribable temperature coefficients that are preferably different from one another.
1. A power supply circuit for producing a reference current with a prescribable temperature dependence, the power supply circuit comprising:
a current mirror outputting a first current and a second current;
a resistor formed by at least two reference resistors having prescribable temperature coefficients that are different from one another; and
two current sinks, each current sink having a terminal of a different size from the other sink, which at their respective input receive the first current or the second current, and in which the current sinks at their respective outputs are connected to a node having a reference potential, the output of at least one current sink being connected via the resistor to the node having the reference potential, wherein a voltage across said resistor is a temperature dependent voltage which has a known value at a reference temperature which known value is proportional to the respective different sizes of each of the terminals of said current sinks wherein the total resistance of said resistor is set to a value at said reference temperature to produce said reference current.
2. The power supply circuit according to claim 1 , wherein the reference resistors are connected to one another in series.
3. The power supply circuit according to claim 1 , wherein at least one of the reference resistors is trimmable.
4. The power supply circuit according to claim 1 , wherein at least one of the reference resistors is a film resistor.
5. The power supply circuit according to claim 1 , wherein the temperature coefficients of the reference resistors have a different sign.
6. The power supply circuit according to claim 1 , wherein the current sinks are field-effect transistors or bipolar transistors and wherein said respective area are gates of said field-effect transistors or emitters areas of said bipolar transistors.
7. The power supply circuit according to claim 1 , wherein the power supply circuit is an integrated circuit.
8. The power supply circuit according to claim 1 ,
wherein the resistor is formed by more than two reference resistors having prescribable temperature coefficients, and
wherein the reference resistors are connected to one another in a combination of series and parallel connections.
9. The power supply circuit according to claim 1 , wherein the reference resistors are connected to one another in parallel.
10. The power supply circuit according to claim 1 , wherein the first input current is equal to the second input current.
11. The power supply circuit according to claim 1 , wherein the output of at least one current sink is connected directly to the node having the reference potential.
12. A power supply circuit for producing a reference current with a prescribable temperature dependence, the power supply circuit comprising:
a first transistor having a terminal area of a first size and having an output, a drain input receiving a first current, and a gate input;
a second transistor having a terminal area of a second size different from said first size and having an output, a drain input receiving a second current, and a gate input; and
a resistor formed by at least two reference resistors having prescribable temperature coefficients that are different from one another;
said first transistor output and said second transistor output being connected to a reference potential, the output of said second transistor being connected to the reference potential via the resistor wherein a temperature dependent voltage across said resistor has a known value at a reference temperature which is proportional to the respective different sizes of each of the terminals of said first and second transistors and wherein the total resistance of said resistor is set to a value at said reference temperature to produce said reference current.
13. The power supply circuit of claim 12 wherein the first resistor has a temperature coefficient having a first sign and the second resistor has a temperature coefficient having a second sign opposite to said first sign.
14. A method of forming a power supply circuit for producing a reference current with a prescribable temperature dependence comprising the steps of:
providing first and second current sinks each having an input and an output said first current sink having a terminal with an area different in size than a corresponding terminal of said second current sink;
providing at least two reference resistors having prescribable temperature coefficients, the prescribable temperature coefficients being different from one another and being selected as a function of the temperature coefficients of power supply circuit components and wherein a voltage across said at least two reference resistors is a temperature dependent voltage which has a known value at a reference temperature which known value is proportional to the respective different sizes of each of the terminals of said current sinks;
connecting the at least two reference resistors in series or parallel to form a control resistor;
providing a first current to the first current sink input;
providing a second current to the second current sink input;
connecting the first current sink output to a reference potential;
connecting the second current sink output to the reference potential via the control resistor;
setting the total resistance of said control resistor to a value corresponding to said reference temperature in order to produce said reference current.
15. The power supply circuit according to claim 1 , wherein each current sink of the two current sinks is a transistor whose control inputs are connected to one another.
16. The power supply circuit according to claim 1 wherein a temperature coefficient of the reference resistors is a function of said temperature dependence of said temperature dependent voltage.
17. The power supply circuit according to claim 12 wherein a temperature coefficient of the reference resistors is a function of said temperature dependence of said temperature dependent voltage.
18. The method according to claim 14 further including providing a temperature coefficient of the reference resistors which is a function of said temperature dependence of said temperature dependent voltage.