ADAPTIVE BIASING SCHEME FOR AN AMPLIFIER

• US 20150145596A1
• Filed: 11/26/2014
• Published: 05/28/2015
• Est. Priority Date: 05/30/2012
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Nujira Limited (Qualcomm, Inc.)
• Inventors: Fagg, Russell
• Granted Patent: US 9,257,941 B2
• Time in Patent Office: Days
• US Class Current: 330/258
• CPC Class Codes: H03F 1/0222 by using a signal derived from the input signal
• CPC Class Codes: H03F 1/0266 by using a signal derived from the input signal
• CPC Class Codes: H03F 1/30 Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters in differential amplifiers H03F3/45479
• CPC Class Codes: H03F 2200/102 A non-specified detector of a signal envelope being used in an amplifying circuit
• CPC Class Codes: H03F 2203/45112 the biasing of the differential amplifier being controlled from the input or the output signal
• CPC Class Codes: H03F 3/45479 characterised by the way of common mode signal rejection

Abstract

There is provided a bias arrangement for an amplifier adapted to amplify a varying input signal, the arrangement comprising a control circuit arranged to adaptively vary a bias current to the amplifier in dependence on an envelope of the varying input signal.

Claims

1. A bias arrangement for an amplifier adapted to amplify a varying input signal, the arrangement comprising:

a current source configured to generate a bias current; and

a control circuit configured to adaptively vary the bias current to the amplifier in dependence on an envelope of the varying input signal, the control circuit including a peak detection circuit configured to track the envelope of the varying input signal and to provide an output, which is proportional to the instantaneous magnitude of the varying input signal, for controlling the variation of the bias current.

2. The bias arrangement of claim 1 wherein the control circuit includes a bias modulation circuit responsive to the output of the peak detection circuit and arranged to control the current source in dependence thereon.

3. The bias arrangement of claim 1 further comprising:

a common mode detection circuit configured to detect a common mode voltage associated with the varying input signal, and

a current generator configured to generate a DC offset current in the bias current in dependence on the detected common mode voltage.

4. The bias arrangement of claim 1 wherein the amplifier is a transconductance amplifier.

5. An envelope-tracking supply for an amplification stage including a transconductance amplifier according to claim 4.

6. A mobile communication handset including an envelope tracking power supply for a radio frequency amplifier including an amplifier according to claim 1.

7. A mobile communication infrastructure device including an envelope tracking power supply for a radio frequency amplifier including an amplifier according to claim 1.

8. A bias arrangement for a transconductance amplifier arranged to amplify a varying input signal, the arrangement comprising:

a peak detection circuit configured to track the envelope of an input signal for the transconductance amplifier and to provide an output which is proportional to the instantaneous magnitude of the input signal; and

a bias modulation circuit responsive to the peak detection circuit and arranged to modulate a bias current to the transconductance amplifier in accordance with the envelope of the input signal.

9. The bias arrangement of claim 8 further comprising a current source for providing the bias current under the control of the bias modulation circuit.

10. A method of providing a bias current to an amplifier arranged to amplify a varying input signal, the method comprising:

(a) varying the bias current in dependence on the envelope of the varying input signal by tracking the envelope of the varying input signal; and

(b) providing an output which is proportional to the instantaneous magnitude of the varying input signal for controlling the variation of the bias current.

11. The method of claim 10 further comprising detecting a common mode voltage associated with the varying input signal, and generating a DC offset current in the bias current in dependence on the detected common mode voltage.

12. The method according to claim 10 applied to a transconductance amplifier.

13. The method according to claim 12 applied to the transconductance amplifier of an envelope tracking power supply for a radio frequency amplifier.