Temperature compensated digital step attenuator
Circuits and methods for eliminating or mitigating the amount of temperature-dependent variation in the relative attenuation of a multi-valued digital step attenuator (DSA) by using resistive components having temperature-dependent resistance values that compensate for or offset changes in the temperature-dependent ON resistance (R ON ) of the switches within the DSA. In some embodiments, DSA attenuator cell switches are fabricated to have positive first-order resistance temperature (FORT) coefficients, while temperature-compensating series attenuation resistances are fabricated as a positive FORT coefficient resistor and temperature-compensating shunt resistances are fabricated as either a negative FORT coefficient resistor or a combination of a negative FORT coefficient resistor in parallel with a positive FORT coefficient resistor.
1. A temperature-compensated attenuator cell, including:
(a) at least one switch, each having a first-order resistance temperature coefficient of a first type; and
(b) at least one resistance element, each coupled to a corresponding switch and having a first-order resistance temperature coefficient of a compensating type with respect to the coupled corresponding switch.
2. A temperature-compensated attenuator cell, including:
(a) a shunt switch having a first-order resistance temperature coefficient of a first type; and
(b) a resistance element coupled to the shunt switch and having a first-order resistance temperature coefficient of a second type complementary to the first-order resistance temperature coefficient of the first type.
3. A temperature-compensated attenuator cell, including:
(a) at least one shunt switch having a first-order resistance temperature coefficient of a first type;
(b) at least one shunt resistance element, each coupled to a corresponding shunt switch and having a first-order resistance temperature coefficient of a second type complementary to the first-order resistance temperature coefficient of the first type;
(c) at least one series resistance element operatively coupled to at least one shunt resistance element in an attenuation configuration and having a first-order resistance temperature coefficient of the first type; and
(d) a series switch coupled in parallel across at least one series resistance and having a first-order resistance temperature coefficient of the first type.
4. A temperature-compensated attenuator cell, including:
(a) at least one shunt switch having a first-order resistance temperature coefficient of a first type;
(b) at least one shunt resistance element, each coupled to a corresponding shunt switch, and each including a first resistor having a first-order resistance temperature coefficient of a second type complementary to the first-order resistance temperature coefficient of the first type, and a second resistor coupled in parallel with the first resistor and having a first-order resistance temperature coefficient of the first type;
(c) at least one series resistance element operatively coupled to at least one shunt resistance element in an attenuation configuration and having a first-order resistance temperature coefficient of the first type; and
(d) a series switch coupled in parallel across at least one series resistance and having a first-order resistance temperature coefficient of the first type.
5. The invention of claims 1 , 2 , 3 , or 4 , wherein the first-order resistance temperature coefficient of the first type is a positive first-order resistance temperature coefficient.
6. The invention of claims 2 , 3 , or 4 , wherein the first-order resistance temperature coefficient of the second type is a negative first-order resistance temperature coefficient.
7. A temperature-compensated digital step attenuator including a least two sequentially-coupled temperature-compensated attenuator cells, each cell including:
(a) at least one switch, each having a first-order resistance temperature coefficient of a first type; and
(b) at least one resistance element, each coupled to a corresponding switch and having a first-order resistance temperature coefficient of a compensating type with respect to the coupled corresponding switch.
8. A temperature-compensated digital step attenuator including a least two sequentially-coupled temperature-compensated attenuator cells, at least one cell including:
(a) a shunt switch having a first-order resistance temperature coefficient of a first type; and
(b) a resistance element coupled to the shunt switch and having a first-order resistance temperature coefficient of a second type complementary to the first-order resistance temperature coefficient of the first type.
9. A temperature-compensated digital step attenuator including a least two sequentially-coupled temperature-compensated attenuator cells, at least one cell including:
(a) at least one shunt switch having a first-order resistance temperature coefficient of a first type;
(b) at least one shunt resistance element, each coupled to a corresponding shunt switch and having a first-order resistance temperature coefficient of a second type complementary to the first-order resistance temperature coefficient of the first type;
(c) at least one series resistance element operatively coupled to at least one shunt resistance element in an attenuation configuration and having a first-order resistance temperature coefficient of the first type; and
(d) a series switch coupled in parallel across at least one series resistance and having a first-order resistance temperature coefficient of the first type.
10. A temperature-compensated digital step attenuator including a least two sequentially-coupled temperature-compensated attenuator cells, at least one cell including:
(a) at least one shunt switch having a first-order resistance temperature coefficient of a first type;
(b) at least one shunt resistance element, each coupled to a corresponding shunt switch, and each including a first resistor having a first-order resistance temperature coefficient of a second type complementary to the first-order resistance temperature coefficient of the first type, and a second resistor coupled in parallel with the first resistor and having a first-order resistance temperature coefficient of the first type;
(c) at least one series resistance element operatively coupled to at least one shunt resistance element in an attenuation configuration and having a first-order resistance temperature coefficient of the first type; and
(d) a series switch coupled in parallel across at least one series resistance and having a first-order resistance temperature coefficient of the first type.
11. The invention of claims 7 , 8 , 9 , or 10 , wherein the first-order resistance temperature coefficient of the first type is a positive first-order resistance temperature coefficient.
12. The invention of claims 8 , 9 , or 10 , wherein the first-order resistance temperature coefficient of the second type is a negative first-order resistance temperature coefficient.