Amplifier gain control circuit for the wireless transceiver

• US 7,701,290 B2
• Filed: 04/03/2008
• Issued: 04/20/2010
• Est. Priority Date: 12/27/2007
• Status: Active Grant

• Current Assignee: Airoha Technology Corporation (MediaTek, Inc.)
• Original Assignee: Airoha Technology Corporation (MediaTek, Inc.)
• Inventors: Liu, Yu-Hua
• Primary Examiner(s): Nguyen; Khanh V
• Application Number:
  US12/078,688
• Publication Number:
  US 20090167574A1
• Time in Patent Office: 747 Days
• Field of Search: 330/254, 330/261, 330/278, 455/127.2, 455/232.1, 455/234.1, 455/245.1
• US Class Current: 330/254
• CPC Class Codes: H03F 2203/45686 the LC comprising one or more potentiometers, which are not shunting potentiometers
• CPC Class Codes: H03F 3/45183 Long tailed pairs H03F3/4521, H03F3/45237 take precedence
• CPC Class Codes: H03F 3/45188 Non-folded cascode stages
• CPC Class Codes: H03G 1/0029 using FETs
• CPC Class Codes: H03M 1/808 using resistors

Abstract

An amplifier gain control circuit for the wireless transceiver comprises at least one amplifier, an analog to digital converter (ADC), a digital to analog converter (DAC) and a bias circuit, wherein the ADC is used for receiving an analog gain control voltage to generate a digital control signal that can be used for controlling the gain of the amplifier, the DAC is used for receiving the digital signal to generate an analog signal, and the bias circuit is used for receiving the analog signal and the analog gain control voltage to further fine-tune the gain of the amplifier by the analog process for correcting the least bit error during the digital process, therefore, the amplifier during the gain adjustment will be prevented to operate in the nonlinear area.

Claims

1. An amplifier gain control circuit for the wireless transceiver, comprising:

at least one amplifier;

an analog to digital converter connected to said amplifier and used for receiving an analog gain control voltage to transform into a digital control signal, wherein the digital control signal is used for controlling the gain of said amplifier by a digital process;

a digital to analog converter connected to said analog to digital converter and used for receiving said digital control signal to transform into an analog signal; and

a bias circuit connected to said digital to analog converter and said amplifier, used for receiving said analog gain control voltage and said analog signal and accordingly providing an analog bias to said amplifier to fine tune and correct the gain of said amplifier by an analog process, such that the least bit error occurred during the gain of said amplifier by the digital process can be corrected.

2. The amplifier gain control circuit of claim 1, wherein said amplifier comprises:

a digital amplifier unit connected to said analog to digital converter and used for receiving said digital control signal; and

an analog amplifier unit connected to said bias circuit and said digital amplifier unit.

3. The amplifier gain control circuit of claim 2, wherein said digital amplifier unit comprises:

a current source;

a first differential unit connected to said current source and used for receiving an input signal;

a second differential unit comprising a first loading element, connected to said first differential unit, used for receiving a first control voltage and a first reference voltage to generating a first output signal; and

a third differential unit comprising a second loading element, connected to said first differential unit, used for receiving a second control voltage and said first reference voltage to generate a second output signal.

4. The amplifier gain control circuit of claim 3, wherein said digital amplifier unit further comprises:

a first control unit connected to said second differential unit for providing said first control voltage; and

a second control unit connected to said third differential unit for providing said second control voltage.

5. The amplifier gain control circuit of claim 4, wherein said first control unit comprises a first switch unit and a first resistor, and said second control unit comprises a second switch unit and a second resistor.

6. The amplifier gain control circuit of claim 5, wherein said first switch unit comprises a plurality of transistors and resistors, wherein said resistors are connected together in series and further connected to the corresponding transistors in parallel.

7. The amplifier gain control circuit of claim 6, wherein said transistor is used for receiving said digital control signal.

8. The amplifier gain control circuit of claim 5, wherein said second switch unit comprises a plurality of transistors and resistors, wherein each resistor is connected together in series and further connected to the corresponding transistor in parallel.

9. The amplifier gain control circuit of claim 8, wherein said transistor is used for receiving said digital control signal.

10. The amplifier gain control circuit of claim 3, wherein said first differential unit comprises at least one switch unit.

11. The amplifier gain control circuit of claim 10, wherein said switch unit comprises a plurality of transistors and resistors, wherein each resistor is connected together in series and further connected to the corresponding transistor in parallel.

12. The amplifier gain control circuit of claim 11, wherein said transistor is used for receiving said digital control signal.

13. The amplifier gain control circuit of claim 2, wherein said bias circuit comprises:

a differential unit connected to a current source, used for receiving said analog gain control voltage and a second voltage reference;

a first current mirror connected to said differential unit, wherein a first node of said first current mirror is connected to a first loading unit and said digital to analog converter; and

a second current mirror connected to said differential unit, wherein a second node of said second current mirror is connected to a second loading unit and said digital to analog converter.

14. The amplifier gain control circuit of claim 13, wherein said digital to analog converter comprises at least one current mirror unit.

15. The amplifier gain control circuit of claim 13, wherein said analog amplifier unit is respectively connected to the first node and the second node of said bias circuit.

16. The amplifier gain control circuit of claim 15, wherein said analog amplifier unit comprises:

a current source;

a first differential unit connected to said current source and used for receiving an input signal;

a second differential unit comprising a first loading element, connected to said first differential unit, the first node and the second node of said bias circuit; and

a third differential comprising a second loading element, connected said first differential unit, the first node and the second node of said bias circuit.