1. A complimentary metal oxide semiconductor variable gain amplifier comprising:
first through fourth transistors which differentially receive first and second input voltages and amplify the first and second input voltages using a predetermined gain;
a transconductance control unit which controls transconductance of fifth and sixth transistors according to a control voltage to control the predetermined gain; and
first and second resistors which generate an output voltage having the predetermined gain according to an output current generated by the fifth and sixth transistors.
2. The complimentary metal oxide semiconductor variable gain amplifier of claim 1, wherein the first through fourth transistors and the fifth and sixth transistors are N-channel metal oxide semiconductor transistors.
3. The complimentary metal oxide semiconductor variable gain amplifier of claim 1, wherein the first through fourth transistors are disposed in parallel, wherein the first and second transistors are configured in a differential input form, and the third and fourth transistors are configured in a differential input form.
4. The complimentary metal oxide semiconductor variable gain amplifier of claim 1, wherein:
the first input voltage is input to gate nodes of the first and third transistors; and
the second input voltage is input to gate nodes of the second and fourth transistors.
5. The complimentary metal oxide semiconductor variable gain amplifier of claim 1, wherein:
drain nodes of the first and fourth transistors are connected to each other and connected to a source node of the fifth transistor; and
drain nodes of the second and third transistors are connected to each other and connected to a source node of the sixth transistor.
6. The complimentary metal oxide semiconductor variable gain amplifier of claim 1, wherein if the first and second input voltages are larger than a first predetermined value, the control voltage is set to be smaller than a second predetermined value, and if the first and second input voltages are smaller than the first predetermined value, the control voltage is set to be larger than the second predetermined value.
7. A complimentary metal oxide semiconductor variable gain amplifier comprising:
first through fourth transistors which differentially receive first and second input voltages and amplify the first and second input voltages using a predetermined gain;
a transconductance control unit which controls transconductance of fifth and sixth transistors according to a control voltage to control the predetermined gain;
a control circuit which differentially receives the control voltage and a bias voltage to generate a mirror current;
seventh and eighth transistors that are current source transistors which supply the mirror current generated by the control circuit to the first through fourth transistors; and
first and second resistors which generate an output voltage having the predetermined gain according to an output current generated by the fifth and sixth transistors.
8. The complimentary metal oxide semiconductor variable gain amplifier of claim 7, wherein the first through fourth transistors, the fifth and sixth transistors, and the seventh and eighth transistors are N-channel metal oxide semiconductor transistors.
9. The complimentary metal oxide semiconductor variable gain amplifier of claim 7, wherein:
source nodes of the first and second transistors are connected to each other and connected to the eighth transistor; and
source nodes of the third and fourth transistors are connected to each other and connected to the seventh transistor.
10. The complimentary metal oxide semiconductor variable gain amplifier of claim 7, wherein the control circuit comprises:
a current source supplying a predetermined current;
a twelfth transistor driven by the bias voltage to supply the current through the current source;
an eleventh transistor driven by the control voltage to supply the current through the current source;
a ninth transistor which supplies the current supplied by the twelfth transistor to the eighth transistor; and
a tenth transistor which supplies the current supplied by the eleventh transistor to the seventh transistor.
11. The complimentary metal oxide semiconductor variable gain amplifier of claim 10, wherein the ninth through twelfth transistors are N-channel metal oxide semiconductor transistors.
12. The complimentary metal oxide semiconductor variable gain amplifier of claim 10, wherein the ninth and tenth transistors are configured in a current mirror form to generate a mirror current.
13. The complimentary metal oxide semiconductor variable gain amplifier of claim 7, wherein:
if the control voltage is smaller than the bias voltage, the current of the eighth transistor is decreased and the current of the seventh transistor is increased to decrease a voltage gain; and
if the control voltage is larger than the bias voltage, the current of the seventh transistor is decreased and the current of the eighth transistor is increased to increase the voltage gain.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. In a computing environment that includes a plurality of objects that are managed according to a plurality of policies, each of which defines an action to be performed and a condition for performing the action, a method for detecting policy conflicts, the method comprising:
receiving a request to create a new policy;
comparing a condition of the new policy with conditions of existing policies that are maintained in a policy storage unit to determine a policy conflict; and
storing the new policy in the policy storage unit if no policy conflict is determined and issuing an error if a policy conflict is determined.
2. The method of claim 1, further comprising:
determining that the condition of the new policy is not in a first format; and
in response to the determination, transforming the condition of the new policy into the first format.
3. The method of claim 2, wherein the step of transforming the condition of the new policy into the first format comprises transforming the condition of the new policy into a negation normal format (NNF).
4. The method of claim 3, wherein the step of transforming the condition of the new policy into the first format further comprises transforming the condition of the new policy into a disjunctive normal format (DNF).
5. The method of claim 4, further comprising applying one or more reduction filters to the transformed condition of the new policy.
6. The method of claim 5, further comprising:
determining that the condition of one or more of the existing policies is not in the first format; and
in response to the determining regarding the existing policies, transforming the conditions of said one or more of the existing policies into the first format.
7. The method of claim 1, wherein the conditions of the new and existing policies each comprises a plurality of terms and the step of comparing the condition of the new policy with the conditions of existing policies comprises:
comparing each term of the condition of the new policy with each term of the conditions of the existing policies.
8. The method of claim 1, wherein the plurality of managed objects includes one or more virtual machines.
9. The method of claim 1, wherein the policy storage unit comprises one or more extended markup language (XML) files.
10. A non-transitory computer readable storage medium having stored thereon computer readable program code for detecting policy conflicts among a plurality of policies that are used to manage a plurality of objects in a computing environment, wherein each policy defines an action to be performed and a condition for performing the action, the computer readable program code comprising:
instructions to receive a request to create a new policy;
instructions to compare a condition of the new policy with conditions of existing policies that are maintained in a policy storage unit to determine a policy conflict; and
instructions to store the new policy in the policy storage unit if no policy conflict is determined and instructions to issue an error if a policy conflict is determined.
11. The computer readable storage medium of claim 10, the computer readable program code further comprising:
instructions to determine that the condition of the new policy is not in a first format; and
in response to the determining, instructions to transform the condition of the new policy into the first format.
12. The computer readable storage medium of claim 11, wherein the instructions to transform the condition of the new policy into the first format comprise instructions to transform the condition of the new policy into a negation normal format (NNF).
13. The computer readable storage medium of claim 12, wherein the instructions to transform the condition of the new policy into the first format further comprise instructions to transform the condition of the new policy into a disjunctive normal format (DNF).
14. The computer readable storage medium of claim 13, the computer readable program code further comprising instructions to apply one or more reduction filters to the transformed condition of the new policy.
15. The computer readable storage medium of claim 14, the computer readable program code further comprising:
instructions to determine that the condition of one or more of the existing policies is not in the first format; and
in response to the determining regarding the existing policies, instructions to transform the conditions of said one or more of the existing policies into the first format.
16. The computer readable storage medium of claim 10, wherein the instructions to compare the condition of the new policy with the conditions of existing policies comprise:
wherein the conditions of the new and existing policies each comprises a plurality of terms, instructions to compare each term of the condition of the new policy with each term of the conditions of the existing policies.
17. The computer readable storage medium of claim 10, wherein the plurality of managed objects includes one or more virtual machines.
18. The computer readable storage medium of claim 10, wherein the policy storage unit comprises one or more extended markup language (XML) files.
19. A computing system configured to detect conflicts among a plurality of policies, comprising:
a plurality of objects;
storage storing a plurality of policies used to manage the plurality of objects; and
a management server configured to:
receive a request to create a new policy;
compare a condition of the new policy with conditions of existing policies that are maintained in the storage to determine a policy conflict; and
store the new policy in the storage if no policy conflict is determined and issue an error if a policy conflict is determined.
20. The computing system of claim 19, wherein the management server is further configured to:
determine that the condition of the new policy is not in a first format; and
in response to the determining, transform the condition of the new policy into the first format.