1. A chopper-stabilized amplifier comprising:
a first amplifier;
a first input chopper circuit having a first input coupled to receive a first input signal, a first output coupled to a first input of the first amplifier, a second output coupled to a second input of the first amplifier, the second input of the first amplifier being coupled to receive a first feedback signal, wherein the first chopper input circuit operates in response to a chopping clock and in response to a chop enable signal;
a first feedback resistor coupled between an output of the first amplifier and the second input of the first amplifier for producing the first feedback signal;
a gain resistor having a first terminal coupled to the second input of the first amplifier and a second terminal coupled to receive a predetermined voltage; and
saturation detection circuitry coupled to a signal path in the chopper-stabilized amplifier for comparing a signal level in the signal path to a reference to generate the chop enable signal if the amplifier is in a normal operating mode and disabling the chop enable signal if the first amplifier is unacceptably close to a saturation condition.
2. The chopper-stabilized amplifier of claim 1 wherein the first input chopper circuit couples a chopped representation of the first feedback signal from a second input of the first chopper circuit to the second input of the first amplifier.
3. The chopper-stabilized amplifier of claim 1 including a chopping enable circuit including an ANDing circuit having a first input for receiving the chopping clock and an enable input for receiving the chop enable signal, and an output for producing an enabled chopping clock signal for controlling chopping switches in the first input chopper circuit.
4. The chopper-stabilized amplifier of claim 1 wherein the first amplifier includes output chopper circuitry coupled to the output of the first amplifier, a first output signal of the chopper-stabilized amplifier being generated by the output chopper circuitry on the output of the first amplifier.
5. The chopper-stabilized amplifier of claim 3 wherein the chopping enable circuit includes circuitry for generating an enabled chopping clock complement signal which is the logical complement of the enabled chopping clock.
6. The chopper-stabilized amplifier of claim 4 wherein the saturation detection circuitry includes a first comparator having a first input coupled to a first reference voltage, a second input coupled to receive the first output signal, and an output coupled to a first input of an ORing circuit having an output on which the chopper enable signal is produced, and a second comparator having a first input coupled to receive the first output signal and a second input coupled to a second reference voltage, and an output coupled to a second input of the ORing circuit.
7. The chopper-stabilized amplifier of claim 4 wherein the saturation detection circuitry includes a first comparator having a built-an offset and having a first input coupled to the first input signal, a second input coupled to receive the first feedback signal, and an output coupled to a first input of an ORing circuit having an output on which the chopper enable signal is produced, and a second comparator having a first input coupled to receive the first feedback signal and a second input coupled to receive the first input signal, and an output coupled to a second input of the ORing circuit.
8. The chopper-stabilized amplifier of claim 6 wherein the first amplifier is powered by a first supply voltage and a second supply voltage, the chopper-stabilized amplifier including a reference circuit including first, second, and third resistors coupled in series between the first supply voltage and the second supply voltage, the first resistor being coupled between the first supply voltage and the second reference voltage, the second resistor being coupled between the second reference voltage and the first reference voltage, and the third resistor being coupled between the first reference voltage and the second supply voltage.
9. The chopper-stabilized amplifier of claim 6 wherein the chopper-stabilized amplifier is a chopper-stabilized instrumentation amplifier including the first amplifier, the first input chopper circuit, the first feedback resistor, the gain resistor, and the saturation detection circuitry, the instrumentation amplifier also including
a second amplifier having an output on which a second output signal is produced;
a second input chopper circuit having a first input coupled to receive a second input signal, a second input coupled to receive a second feedback signal, a first output coupled to a first input of the second amplifier, a second output coupled to a second input of the second amplifier, wherein the second input chopper circuit operates in response to the chopping clock and in response to the chop enable signal;
a second feedback resistor coupled between an output of the second amplifier and the second input of the second input chopper circuit for producing the second feedback signal;
the second terminal of the gain resistor being coupled to the second input of the second input chopper circuit; and
the saturation detection circuitry including a third comparator having a first input coupled to receive the second output signal, a second input coupled to the second reference voltage, and an output coupled to a third input of the ORing circuit, the saturation detection circuitry also including a fourth comparator having a first input coupled to receive the first reference voltage, a second input coupled to receive the second output signal, and an output coupled to a fourth input of the ORing circuit.
10. The chopper-stabilized amplifier of claim 8 wherein the first reference voltage is approximately a millivolt greater than the second supply voltage and the second reference voltage is approximately a millivolt less than the first supply voltage.
11. The chopper-stabilized amplifier of claim 5 wherein the input chopper circuit includes first, second, third, and fourth switches, the first switch being controlled by the enabled chopping clock signal and having a first terminal, and also having a second terminal coupled to the second input of the first amplifier, the second switch being controlled by the enabled chopping clock signal and having a first terminal, and also having a second terminal coupled to the first input of the first amplifier, an input difference signal being applied between the first terminals of the first and second switches, the third switch being controlled in accordance with the enabled chopping clock complement signal and having a first terminal coupled to the first terminal of the first switch and a second terminal coupled to the first input of the first amplifier, the fourth switch being controlled in accordance with the enabled chopping clock complement signal and having a first terminal coupled to the first terminal of the third switch and a second terminal coupled to the second input of the first amplifier.
12. The chopper-stabilized amplifier of claim 9 wherein the first and second amplifiers are transconductance amplifiers.
13. The chopper-stabilized amplifier of claim 9 wherein the first, second, third, and fourth comparators have lower offset and higher bandwidth than the first and second amplifiers.
14. The chopper-stabilized amplifier of claim 9 wherein the predetermined voltage is a fixed reference voltage.
15. A method for reducing input leakage current in a chopper-stabilized amplifier including an amplifier, an input chopper circuit having a first input coupled to receive an input signal, and an output coupled to a first input of the amplifier, a feedback resistor being coupled to an output of the amplifier to couple a feedback signal to a second input of the amplifier, the chopper-stabilized amplifier producing an output signal, wherein the input chopper circuit operates in response to a chopping clock, the method comprising:
operating the chopper-stabilized amplifier in a normal mode;
determining if the amplifier is unacceptably close to a saturation condition by comparing a signal level in a signal path of the chopper-stabilized amplifier to a reference value; and
disabling the chopping clock if the amplifier is determined to be unacceptably close to the saturation condition.
16. The method of claim 15 including logically ANDing the chopping clock and a chop enable signal to produce an enabled chopping clock signal for controlling chopping switches in the input chopper circuit during the operation in the normal mode.
17. The method of claim 16 wherein step (c) includes comparing a difference between a first reference voltage and the first output signal and disabling the enabled chopping clock signal if that difference is positive, and comparing a difference between the first output signal and a second reference voltage and disabling the enabled chopping clock signal if that difference is positive.
18. The method of claim 17 wherein the first reference voltage is approximately a millivolt greater than a low side supply voltage of the amplifier and the second reference voltage is approximately a millivolt less than a high side supply voltage of the amplifier.
19. The method of claim 16 including generating an enabled chopping clock complement signal in response to the enabled chopping clock and controlling some of the chopping switches directly in response to the enabled chopping clock complement signal.
20. (canceled)
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. A method of determining whether an outdial call is authorized, comprising:
electronically obtaining a call criterion from a request to authorize an outdial communication service call initiated by a message center in response to an indial call received at the message center, the call criterion determined from an access number used to route the indial call to the message center, the outdial communication service call to be authorized based on the call criterion; and
electronically retrieving an authorization result based on the call criterion by accessing a data structure that correlates a plurality of authorization results with a plurality of call criteria, wherein each of the plurality of authorization results is selectively modifiable.
2. A method as defined in claim 1, further comprising retrieving a routing rule based on the call criterion, wherein the routing rule indicates information necessary for establishing the outdial communication service call.
3. A method as defined in claim 2, wherein the routing rule indicates a local access transport area from which the outdial communication service call may be routed.
4. A method as defined in claim 3, further comprising selecting a communications path located in the local access transport area based upon at least one of a communications path type, a subscriber group identifier, a distance criteria, an outdial call type criteria, a subscriber type criteria, a communication path load, a communication path utilization, an outdial communication service type, or a feature.
5. A method as defined in claim 2, wherein the routing rule indicates an ordered list of local access transport areas from which the outdial call may be routed.
6. A method as defined in claim 1, further comprising providing an authorization status associated with the outdial communication service call to a requesting server.
7. A method as defined in claim 1, wherein retrieving the authorization result based on the call criterion comprises:
determining a first index based upon a portion of the call criterion;
determining a second index based upon a second portion of the call criterion; and
retrieving the authorization result based on the first and the second indices.
8. A method as defined in claim 1, wherein retrieving the authorization result based on the first and the second indices comprises accessing an authorization and routing rules table.
9. A method as defined in claim 8, wherein the authorization and routing rules table comprises an authorization results section and a routing rules section.
10. A method as defined in claim 9, wherein the authorization results section contains a plurality of columns, wherein each of the columns is associated with a feature type.
11. A method as defined in claim 9, wherein the routing rules results section contains a plurality of columns, wherein each of the columns is associated with a feature type.
12. A method as defined in claim 9, wherein the authorization results section contains a regulatory rules column, a business rules column and an exception column.
13. A method as defined in claim 9, wherein the routing rules results section contains a plurality of columns, wherein each of the columns is associated with a feature type.
14. A method as defined in claim 1, wherein retrieving the authorization result based on the call criterion by accessing the data structure comprises:
retrieving at least one of an authorization rule or an exception based on the call criteria; and
determining the authorization result from the at least one of the authorization rule or the exception.
15. A method as defined in claim 14, wherein the authorization rule is at least one of a regulatory authorization rule or a business authorization rule.
16. A method as defined in claim 15, wherein the business authorization rule conforms to at least one of a regulatory rule, a regulatory law or a regulatory constraint.
17. A method as defined in claim 14, wherein the exception indicates that a communication service type that is indicated allowable by the authorization rule is unallowable unless at least one condition is met.
18. A method as defined in claim 14, further comprising obtaining a routing rule associated with the call criterion, wherein the routing rule indicates at least one local access transport area from which the outdial call may be routed.
19. A method as defined in claim 14, further comprising obtaining a routing rule associated with the call criterion, wherein the routing rule indicates an ordered list of local access transport areas from which the outdial call may be routed.
20. A method as defined in claim 1, wherein the call criterion comprises at least one of an outdial call type criterion, a distance type criterion, a subscriber type criterion, a feature type criterion, or a circuit type criterion.
21. A method as defined in claim 20, wherein at least one of the distance type criterion, the subscriber type criterion or the circuit type criterion are based on an access number associated with the outdial call.
22. A method as defined in claim 1, further comprising requesting a calling card access number if the authorization result requires a calling card access number.
23. An outdial authorizer, comprising:
an authorization request interface to receive a request to authorize an outdial communication service call;
a criterion parser to obtain a call criterion from the request, the call criterion determined from an access number used to route an indial call to a message center that is to initiate the outdial communication service call; and
an analyzer to make a first authorization determination based on a subscriber type, a circuit type and a distance type, and to make a second authorization determination based on the first authorization determination and a feature type to determine if the outdial communication service call is authorized, at least one of the first authorization determination or the second authorization determination being based on the call criterion.
24. An outdial authorizer as defined in claim 23, further comprising:
an authorization interface to retrieve at least one of an authorization rule or an exception associated with the outdial communication service call based on the call criterion, wherein the analyzer uses the at least one the authorization rule or the exception to determine if the outdial communication service call is authorized.
25. An outdial authorizer as defined in claim 24, wherein the authorization rule includes at least one of a regulatory authorization rule or a business authorization rule.
26. An outdial authorizer as defined in claim 24, wherein the authorization interface retrieves an exception associated with the outdial communication service call based on the call criterion, wherein the exception indicates that a communication service type that is indicated allowable by the authorization rule is unallowable unless at least one condition is met.
27. An outdial authorizer as defined in claim 24, further comprising a memory having at least one data structure stored thereon to store the authorization rule and the exception, wherein the data structure correlates a plurality of authorization rules and a plurality of exception with one or more call criteria.
28. An outdial authorizer as defined in claim 27, wherein each of the plurality of authorization rules and each of the plurality of exceptions may be modified in the data structure without modifying the other ones of the plurality of authorization rules and the other ones of the plurality of exceptions.
29. An outdial authorizer as defined in claim 23, further comprising an authorization interface to retrieve a routing rule associated with the outdial communication service call based on the call criterion, wherein the routing rule indicates routing information to establish the outdial communication service call.
30. An outdial authorizer as defined in claim 23, wherein the analyzer determines whether a calling card access number is required to authorize the outdial communication service call based on the authorization rule.
31. An outdial authorizer as defined in claim 23, further comprising a memory having at least one data structure stored thereon to store the authorization result, wherein the data structure correlates a plurality of authorization results with one or more call criteria.
32. An outdial authorizer as defined in claim 31, wherein each of the plurality of authorization results may be modified in the data structure without modifying the other ones of the plurality of authorization results.
33. A communication network, comprising:
an application server to initiate an outdial communication service call by communicating an authorization request associated with the outdial communication service call; and
a policy server including an outdial authorizer to receive the authorization request and to make a first authorization determination based on a subscriber type, a circuit type and a distance type, and to make a second authorization determination based on the first authorization determination and a feature type to determine an authorization for the outdial communication service, at least one of the first authorization determination or the second authorization determination being based on a call criterion contained in the request, the call criterion determined from an access number used to route an indial call to the application server, the access number not identifying where the indial call originated.
34. A communication network as defined in claim 33, wherein the outdial authorizer determines whether a calling card access number is required to authorize the outdial communication service call.
35. A communication network as defined in claim 33, wherein the policy server communicates whether or not the outdial communication service is authorized to the application server.
36. A communication network as defined in claim 33, wherein the policy server communicates a route if the outdial communication service is authorized.