Methods and apparatus for amplification in a tuner

• US 7,091,792 B2
• Filed: 05/20/2004
• Issued: 08/15/2006
• Est. Priority Date: 05/20/2004
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Mehr, Iuri
• Primary Examiner(s): Choe, Henry
• Application Number:
  US10/849,738
• Publication Number:
  US 20050258904A1
• Time in Patent Office: 817 Days
• Field of Search: 330/305, 330/124.R, 330/295, 330/51, 330/279, 330/254
• US Class Current: 330/305
• CPC Class Codes: H03F 2200/294 the amplifier being a low noise amplifier [LNA]
• CPC Class Codes: H03F 2200/331 Sigma delta modulation being used in an amplifying circuit
• CPC Class Codes: H03F 2200/372 Noise reduction and elimination in amplifier
• CPC Class Codes: H03F 3/189 High-frequency amplifiers, e.g. radio frequency amplifiers
• CPC Class Codes: H03F 3/72 Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal

Abstract

Methods and apparatus for amplifying a tuner input signal are disclosed. One embodiment of the invention is directed to a tuner amplifier system comprising a tuner amplifier input that receives a tuner amplifier input signal and a first amplifier comprising an input and an output. The input of the first amplifier is coupled to the tuner amplifier input. The system further comprises a second amplifier comprising an input and an output, the input of the second amplifier being coupled to the tuner amplifier input, and a switch adapted to couple one of the first amplifier output and the second amplifier output to an output of the tuner amplifier. Another embodiment of the invention is directed to a method of amplifying a tuner input signal. The method comprises acts of detecting a power of the tuner input signal, selecting a tuner amplifier to amplify the tuner input signal based on the power of the tuner input signal, and amplifying the tuner input signal using the selected amplifier.

Claims

1. A tuner amplifier system, comprising:

a tuner amplifier input that receives a tuner amplifier input signal;

a first amplifier comprising an input and an output, the input of the first amplifier being coupled to the tuner amplifier input;

a second amplifier comprising an input and an output, the input of the second amplifier being coupled to the tuner amplifier input, wherein the second amplifier is a variable gain amplifier;

a tuner amplifier output that transmits a tuner amplifier output signal; and

at least one switch adapted to select a pathway from which the tuner amplifier output signal is received, wherein the pathway comprises one of the first amplifier and the second amplifier.

2. The tuner amplifier system of claim 1, wherein the at least one switch comprises a first input coupled to the output of the first amplifier, a second input coupled to the output of the second amplifier, and an output, wherein the switch is adapted to couple one of the first and second inputs of the switch to the output of the switch.

3. The tuner amplifier system of claim 1, wherein the at least one switch comprises a plurality of switches.

4. The tuner amplifier system of claim 1, wherein the at least one switch is incorporated within at least one of the first and second amplifiers.

5. The tuner amplifier system of claim 1, wherein the at least one switch is further adapted to select the pathway from which the tuner amplifier output signal is received in response to a detected power.

6. The tuner amplifier system of claim 5, wherein the second amplifier further comprises at least one transconductance amplifier having a transconductance that is responsive to an indication of the detected power.

7. The tuner amplifier system of claim 6, wherein a transconductance of each of the at least one transconductance amplifier has a transconductance that is independently variable.

8. The tuner amplifier system of claim 5, wherein the at least one switch is further adapted to select the pathway from which the tuner amplifier output signal is received in response to a detected power of a signal at the output of the tuner amplifier.

9. The tuner amplifier system of claim 8, wherein the signal at the output of the tuner amplifier is a broadband signal.

10. The tuner amplifier system of claim 8, wherein the at least one switch is adapted to select the pathway as a pathway comprising the first amplifier in response to detecting a power level that is less than a first value and select the pathway as a pathway comprising the second amplifier in response to detecting a power level that is greater than a second value, wherein the first value is larger than the second value.

11. The tuner amplifier system of claim 8, wherein the at least one switch is adapted to select the pathway from which the tuner amplifier output signal is received in response to a hysteresis function.

12. The tuner amplifier system of claim 1, wherein the at least one switch is further adapted to select the pathway as a pathway comprising the first amplifier when a power of the tuner amplifier input signal is within a first range and select the pathway as a pathway comprising the second amplifier when the power of the tuner amplifier input signal is within a second range.

13. The tuner amplifier system of claim 12, wherein the at least one switch is adapted to select the pathway as a pathway comprising the first amplifier when the power of the tuner amplifier input signal is between approximately −

85 dBm and a selected value.

14. The tuner amplifier system of claim 12, wherein the at least one switch is adapted to select the pathway as a pathway comprising the second amplifier when the power of the tuner amplifier input signal is between the selected value and approximately +9 dBm.

15. The tuner amplifier system of claim 1, wherein the first amplifier is a fixed gain amplifier and the second amplifier is a variable gain amplifier.

16. The tuner amplifier system of claim 15, wherein an impedance network of the first amplifier comprises active elements.

17. The tuner amplifier system of claim 15, wherein a noise figure of the first amplifier is equal to or less than approximately 5 dB.

18. The tuner amplifier system of claim 15, wherein an impedance network of the second amplifier includes substantially no active elements.

19. The tuner amplifier system of claim 15, wherein a gain of the first amplifier is approximately equal to a maximum gain of the second amplifier.

20. The tuner amplifier system of claim 15, further comprising:

a power detector coupled to the output of the tuner amplifier; and

a gain controller coupled to the second amplifier to control the gain of the second amplifier in response to an indication of power generated by the power detector.

21. The tuner amplifier system of claim 20, wherein the power detector generates an indication of peak power.

22. The tuner amplifier system of claim 20, wherein the power detector generates an indication of RMS power.

23. The tuner amplifier system of claim 20, wherein the at least one switch is adapted to select the pathway as a pathway comprising the first amplifier in response to the indication of power being less than a first value and select the pathway as a pathway comprising the second amplifier in response to the indication of power being greater than a second value, wherein the first value is greater than the second value.

24. The tuner amplifier system of claim 20, further comprising:

an image filter coupled between the output of the tuner amplifier and the power detector.

25. The tuner amplifier system of claim 1, wherein the tuner amplifier input receives a television signal.

26. The tuner amplifier system of claim 1, wherein the first amplifier comprises a differential input and a differential output.

27. The tuner amplifier system of claim 1, wherein the second amplifier comprises a differential input and a differential output.