Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
  • H03F3/45—Differential amplifiers
  • H03F3/45071—Differential amplifiers with semiconductor devices only
  • H03F3/45076—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier
  • H03F3/45475—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier using IC blocks as the active amplifying circuit

Definitions

• the invention relates generally to an amplifier and, more particularly, to an active mute scheme for an amplifier.
• Muting circuitry is commonly employed with audio and other amplifiers.
• a example embodiment of the invention accordingly, provides an apparatus.
• the apparatus comprises a first pin; a second pin; a third pin; an amplifier having a first input terminal, a second input terminal, and an output terminal, wherein the output terminal of the amplifier is coupled to the third pin; a first switch network that is coupled between the first pin and the first input terminal of the amplifier and that is coupled between the second pin and the second input terminal of the amplifier; a second switch network that is coupled to the first input terminal of the amplifier, the second input terminal of the amplifier, and the output terminal of the amplifier; and a controller that is coupled to provide a first control signal to the first switch network and that is coupled to provide a second control signal to the second switch network, wherein the first control signal activates each switch in the first switch network during an amplify mode and a transition mode, and wherein the second control signal activates each switch in the second switch network during a mute mode and the transition mode, and wherein feedback through the amplifier during the mute mode actively mutes the amplifier.
• the amplifier further comprises a class AB audio amplifier.
• first switch network further comprises: a first switch that is coupled between the first pin and the first input terminal of the amplifier, wherein the first switch is controlled by the first control signal; and a second switch that is coupled between the second pin and the second input terminal of the amplifier, wherein the second switch is controlled by the first control signal.
• the first and second switches further comprise MOSFET switches.
• rise and fall times for the first control signal are about 30 ⁇ 8.
• the second switch network further comprises: a first switch that is coupled between the output terminal of the amplifier and the first input terminal of the amplifier, wherein the first switch is controlled by the second control signal; and a second switch that is coupled between the second input terminal of the amplifier and ground, wherein the second switch is controlled by the second control signal.
• the second switch network further comprises a resistor that is coupled between the first switch and the first input terminal of the amplifier.
• the resistor further comprises a first resistor
• the second switch network further comprises: a third switch that is coupled to the first input terminal of the amplifier, wherein the third switch is controlled by the second control signal; and a second resistor that is coupled between the third switch and ground.
• the first and second resistor each have a resistance of about 10kQ.
• the first, second, and third switches further comprise MOSFET switches.
• rise and fall times for the second control signal are about 30 ⁇ 8.
• the length of the transition mode is at least about 100 ⁇ 8.
• an apparatus comprising a first pin; a second pin; a third pin; an amplifier having a first input terminal, a second input terminal, and an output terminal, wherein the output terminal of the amplifier is coupled to the third pin; a first switch network having: a first switch that is coupled between the first pin and the first input terminal of the amplifier; and a second switch that is coupled between the second pin and the second input terminal of the amplifier; a second switch network having: a third switch that is coupled to the output terminal of the amplifier; a fourth switch that is coupled between the second input terminal of the amplifier and ground; a first resistor that is coupled between the first switch and the first input terminal of the amplifier; a fifth switch that is coupled to the first input terminal of the amplifier; and a second resistor that is coupled between the third switch and ground; and a controller that is coupled to provide a first control signal to the first and second switches and that is coupled to provide a second control signal to the third, fourth, and fifth switches,
• a method comprises activating a plurality of switches in a first switch network with a first control signal during an active mode so as to amplify a signal from a signal source with an amplifier; activating a plurality of switches in a second switch network with a second control signal during a transition mode to retain closed loop operation of the amplifier; and deactivating the plurality of switches in the first switch network with the first control signal during a mute mode so that feedback through the amplifier actively mutes the amplifier, wherein the mute mode follows the transition mode.
• FIG. 1 is a block diagram of an example of a circuit in accordance with an example embodiment of the invention.
• FIG. 2 is a timing diagram for the control signals of the circuit of FIG. 1.
• the reference numeral 100 generally designates a circuit in accordance with an example embodiment of the invention.
• Circuit 100 generally comprises an integrated circuit (IC) 102 and resistors R3, R4, R5, and R6. Resistors R3, R4, R5, and R6 are coupled to pins 108, 110, and 112 of IC 102 in order to amplify input signal AIN so as generate output signal OUT.
• IC 102 generally comprises switch networks, amplifier 104 (which is typically a class AB audio amplifier), and controller 106.
• IC 102 generally operates the amplifier 104 in three modes: active mode, transition mode, and mute mode. Each of these modes can be seen in FIG. 2.
• active mode which is shown between times tO and tl of FIG. 2
• control signal CNTL2 is asserted by controller 106 so that switches SI and S2 (of one of the switch networks) are activated.
• switches SI and S2 are activated, the amplifier 104 normally amplifies the input signal AIN.
• control signals CNTL1 and CNTL2 are both asserted by controller 106 to activate switches SI through S5 (of all of the switch networks).
• the transition mode (which is generally at least about 100 ⁇ 8 in length) is provided to maintain closed loop operation of amplifier 104; without the transition mode, the amplifier 104 would generate audible artifacts (for audio applications) associated with open loop operation.
• control signal CNTL1 is asserted to activate switches S3, S4, and S5 (of one of the switch networks). Switches S3, S4, and S5 enable the positive input terminal of amplifier 104 to be grounded while feedback from the output terminal of amplifier 104 can be provided through resistors Rl and R2 (which are each generally about 10kQ) to the negative input terminal of amplifier 104. This feedback actively mutes the amplifier 104 by driving the output signal OUT to null or ground with an attenuation of about 70-80dB or higher.
• each switch SI through S5 is generally a MOSFET switch. This means that charge injection from these switches SI through S5 should be considered for the relative sizes of switches SI through S5 and rise/fall times of control signals CNTL1 and CNTL2. Typically, the rise and fall times for control signals CNTL1 and CNTL2 (as shown between times tl to t2 and times t3 to t4 in FIG. 2) are about 30 ⁇ 8. Additionally, dummy switches can be employed for switch injection cancellation.

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Amplifiers (AREA)
• Control Of Amplification And Gain Control (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=44708926

Family Applications (1)

Country Status (4)

Families Citing this family (2)

Citations (4)

Family Cites Families (6)

• 2010
  • 2010-03-30 US US12/750,431 patent/US8138828B2/en active Active
  • 2010-12-21 JP JP2013502558A patent/JP5822912B2/ja active Active
  • 2010-12-21 CN CN201080065294.6A patent/CN102792587B/zh active Active
  • 2010-12-21 WO PCT/US2010/061431 patent/WO2011126525A1/en not_active Ceased

Patent Citations (4)

Also Published As

Similar Documents

Legal Events