Audio amplification circuit capable of automatically switching gains

Abstract

The utility model discloses an audio amplification circuit capable of automatically switching gains, and relates to the technical field of electronics, in particular to an audio amplification circuit capable of automatically switching gains, which comprises a second amplification module, a first amplification module, a first input end, a second input end and a second control end, the cathode input end of the second amplification unit is connected with the drain electrode or the source electrode of the first triode, and the anode input end is connected with the source electrode or the drain electrode of the second triode; grid electrodes of the first triode and the second triode are respectively connected with the second control end; the first input end is connected with the anode input end of the second amplification unit; the first amplification module comprises a first amplification unit, the positive electrode input end of the first amplification unit is connected with the second input end and the output end of the second amplification unit, the circuit can achieve functions only through a simple transistor and an integrated operational amplifier, the cost of a system is reduced, the packaging area is also reduced, and the reliability of the system is improved. And meanwhile, the scheme does not need complex components, and is relatively simple to implement.

Description

Technical Field

[0001] The present application relates to the field of electronic technology, and in particular to an audio amplifier circuit capable of automatically switching gain. Background Art

[0002] Existing technologies mainly use "software setting switch + hardware operational amplification" or "hardware setting switch + software operational amplification" to simultaneously realize the audio switching and amplification functions. For example, the chip allows the gain to be set by software, or the switch can be set by software.

[0003] In scenarios where gain and switching cannot be set through software, analog switch chips and op amps are often connected in series to achieve amplification and audio switching circuits. However, there are still the following disadvantages: the switch chips used are expensive, and the PCB layout increases due to the addition of chips. Utility Model Content

[0004] The purpose of the utility model is to avoid the shortcomings of the prior art and provide a technology of a self-switching amplifier circuit which can reduce both the system and the packaging area.

[0005] The purpose of the utility model is achieved through the following technical solutions:

[0006] An audio amplifier circuit capable of automatically switching gain comprises: a second amplifier module, a first amplifier module, a first input end, a second input end and a second control end, wherein the first input end, the second input end and the second control end are respectively used to receive a first audio signal, a second audio signal and a second level signal; the second amplifier module comprises: a second amplifier unit, a first triode and a second triode; the negative input end of the second amplifier unit is connected to the drain or source of the first triode, and the positive input end is connected to the source or drain of the second triode; the gates of the first triode and the second triode are respectively connected to the second control end; the first input end is connected to the positive input end of the second amplifier unit; the first amplifier module comprises a first amplifier unit, and the positive input end of the first amplifier unit is respectively connected to the second input end and the output end of the second amplifier unit.

[0007] Specifically, it also includes: a power supply module; the power supply module is used to output a working voltage, and is used to power the second amplification module and the first amplification module; wherein the source or drain of the first transistor is connected to the working voltage and is connected to the second control terminal.

[0008] More specifically, it also includes: an external module and an MCU; the external module is used to output a first level signal and a second audio signal; the MCU is used to output the first audio signal, and generate and output a second level signal according to the first level signal.

[0009] More specifically, the external module includes a level output pin and a power access pin; the power access pin is used to access the working voltage; the level output pin is used to output a first level signal; when the external module is not connected to an external device, the level output pin and the power access pin are connected; when the external module is connected to an external device, the level output pin is disconnected from the power access pin.

[0010] The above also includes: a first voltage-dividing resistor; a first end of the first voltage-dividing resistor is connected to the first input end, and a second end of the first voltage-dividing resistor is connected to the positive input end of the second amplifying unit.

[0011] More specifically, the first end of the first voltage-dividing resistor is connected to the drain or source of the first transistor; the second end of the first voltage-dividing resistor is connected to the source or drain of the second transistor.

[0012] More specifically, the drain or source of the second transistor is grounded, and the gate is connected to the drain or source.

[0013] In another specific embodiment, the first transistor is a P-channel MOS transistor; and the second transistor is an N-channel MOS transistor.

[0014] Another specific embodiment further includes a first filtering unit and a second filtering unit; the two ends of the first filtering unit are connected to the negative input terminal and the output terminal of the first amplifying unit; the two ends of the second filtering unit are connected to the negative input terminal and the output terminal of the second amplifying unit.

[0015] More specifically, the first filtering unit includes a first resistor and a first capacitor connected in parallel; the second filtering unit includes a second resistor and a second capacitor connected in parallel.

[0016] The beneficial effects achieved by the utility model are as follows: an audio amplifier circuit capable of automatically switching gain comprises: a second amplifier module, a first amplifier module, a first input terminal, a second input terminal and a second control terminal, wherein the first input terminal, the second input terminal and the second control terminal are respectively used to access a first audio signal, a second audio signal and a second level signal; the second amplifier module comprises: a second amplifier unit, a first triode and a second triode; the negative input terminal of the second amplifier unit is connected to the drain or source of the first triode, and the positive input terminal is connected to the source or drain of the second triode; the gates of the first triode and the second triode are respectively connected to the second control terminal; the first input terminal is connected to the positive input terminal of the second amplifier unit; the first amplifier module comprises the first amplifier unit, and the positive input terminal of the first amplifier unit is respectively connected to the second input terminal and the output terminal of the second amplifier unit. The circuit only needs simple transistors and integrated operational amplifiers to realize the function, which reduces the cost of the system and the packaging area. At the same time, the scheme does not require complex components and is relatively simple to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, a brief introduction will be given below to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 It is a circuit principle schematic diagram of an audio amplifier circuit capable of automatically switching gain according to an embodiment of the present application. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described through the implementation method with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0020] Example 1

[0021] One of the implementation methods of the audio amplifier circuit capable of automatically switching gain of the present application is as follows: Figure 1 As shown, it includes: a first amplifying module, a second amplifying module, a first input end, a second input end and a second control end. The first input end, the second input end and the second control end are respectively used to access the first audio signal MCU_IN1, the second audio signal MCU_IN2 and the second level signal MCU_IO2.

[0022] In this embodiment, a dual-channel integrated operational amplifier is used, and two operational amplifier units ( Figure 1 U1A and U1B) in the figure correspond to the first amplifying module and the second amplifying module respectively.

[0023] The second amplifying module includes: a second amplifying unit U1 B, a first triode Q1 and a second triode Q2; the negative input terminal of the second amplifying unit U1 B is connected to the drain or source of the first triode Q1, and the positive input terminal is connected to the source or drain of the second triode Q2; the gates of the first triode Q1 and the second triode Q2 are respectively connected to the second control terminal; and the first input terminal is connected to the positive input terminal of the second amplifying unit U1 B.

[0024] The first amplifying module includes a first amplifying unit U1A, and a positive input terminal of the first amplifying unit U1A is connected to the second input terminal MCU_IN2 and an output terminal of the second amplifying unit U1B respectively.

[0025] Specifically, an audio amplifier circuit capable of automatically switching gain in the present application also includes: a power supply module; the power supply module is used to output a 3.3V operating voltage, which is used to power the second amplifier module and the first amplifier module; wherein the drain or source of the first transistor Q1 is connected to the operating voltage and is connected to the second control terminal.

[0026] More specifically, an audio amplifier circuit capable of automatically switching gain of the present application further includes: a first voltage-dividing resistor R11; a first end of the first voltage-dividing resistor R11 is connected to the first input end, and a second end of the first voltage-dividing resistor R11 is connected to the positive input end of the second amplifying unit U1 B.

[0027] More specifically, the first end of the first voltage-dividing resistor R11 is connected to the drain or source of the first transistor Q1. The second end of the first voltage-dividing resistor R11 is connected to the source or drain of the second transistor Q2. The drain or source of the second transistor Q2 is grounded, and the gate is connected to the drain or source.

[0028] In this embodiment, the first transistor Q1 is a P-channel MOS transistor; the second transistor is an N-channel MOS transistor. The first end of the first voltage-dividing resistor R11 is connected to the drain of the first transistor Q1 after passing through the resistor R10 and the resistor R5 in sequence; the second end of the first voltage-dividing resistor R11 is connected to the source of the second transistor Q2. The source of the first transistor Q1 is connected to the working voltage and is connected to the second control terminal through the resistor R4. The drain of the second transistor Q2 is grounded; the gate of the second transistor Q2 is grounded (or connected to the drain of the second transistor Q2) through the resistor R16, and at the same time, the gate of the second transistor Q2 is connected to the second control terminal through the resistor R15.

[0029] More specifically, an audio amplifier circuit capable of automatically switching gain of the present application further includes a first filter unit and a second filter unit; two ends of the first filter unit are connected to the negative input terminal and the output terminal of the first amplifier unit U1A;

[0030] Two ends of the second filter unit are connected to the negative input end and the output end of the second amplifying unit U1 B. The first filter unit includes a first resistor R1 and a first capacitor C1 connected in parallel; the second filter unit includes a second resistor R2 and a second capacitor C2 connected in parallel.

[0031] More specifically, the audio amplifier circuit capable of automatically switching gain of the present application further includes: an external module and an MCU. The external module is used to output a first level signal MCU_IO1 and a second audio signal MCU_IN2.

[0032] The MCU is connected to a microphone core, and is used to generate and output a first audio signal MCU_IN1 according to a signal collected by the microphone core, and to generate and output a second level signal MCU_IO2 according to the acquired first level signal MCU_IO1.

[0033] In this embodiment, the external module is an audio socket J1 using a 3.5mm input interface. The audio socket J1 includes a level output pin (pin 3 in the figure) and a power access pin (pin 5 in the figure); the power access pin 3 is used to access the working voltage; the level output pin 5 is used to output a first level signal. When the external module is not connected to an external device, the level output pin 3 and the power access pin 5 are connected, and the first level signal MCU_IO1 output by the level output pin 3 is a high level (3.3V); when the external module is connected to an external device, the level output pin 3 is disconnected from the power access pin 5, and the first level signal MCU_IO1 output by the level output pin 3 is a low level (0V).

[0034] Specific working principle:

[0035] When the external module is not connected to an external device (such as a headset with a microphone), the potential of the first level signal MCU_IO1 is close to 3.3V and the state is high. At this time, the MCU configures the second level signal MCU_IO2, so that the second level signal MCU_IO2 outputs a low level. The first transistor Q1 is a P-channel MOS tube, and the Vgs (th) of the MOS tube is -0.55V; since the gate potential of the first transistor Q1 is 0 and the drain potential is 3.3V, the Vgs voltage is -3.3V at this time, which meets the conduction condition. The 3.3V working voltage can provide a normal bias voltage to the second amplifier module through the first transistor Q1 for amplification. The second transistor Q2 is an N-channel MOS tube, and the Vgs (th) of the MOS tube is 0.95V. Since the gate potential is close to 0 and the source potential is also 0, the second transistor Q2 is not turned on. At this time, the second audio signal MCU_IN2 has no audio output, which will not affect the audio amplification effect of the first audio signal MCU_IN1.

[0036] When the earphone is inserted, the audio socket J1 is no longer connected between pins 3 and 5 because of the insertion of the earphone. At this time, the potential of the first level signal MCU_IO1 is close to 0. The MCU detects that the first level signal MCU_IO1 is low, and then configures the second level signal MCU_IO2 to output a high level. At this time, the gate potential of the first transistor Q1 is 3.3V, the source voltage is 3.3V, and the Vgs voltage is 0V, which does not meet the conduction condition. Therefore, 3.3V cannot pass through the first transistor Q1 normally, and cannot provide a bias voltage to the second amplifier module. Therefore, the audio of this channel cannot be amplified normally and is isolated at the in-phase input end. At the same time, the gate potential of the second transistor Q2 is also 3.3V, and the source ground potential is 0V, so Vgs is 3V, which is greater than Vgs(th), and the second transistor Q2 is turned on. Due to the existence of the voltage-dividing resistor R11, combined with the voltage division of the on-resistance (about 45-70mΩ) of Q2 inside the second transistor, the audio input to the second amplifier module is divided to an infinitely small voltage, and even if it passes through the first amplifier unit U1A later, it will not be affected and will not produce a sound leakage effect. The audio input to the second amplifier module can normally enter the same-direction input terminal through the bias voltage of the first amplifier module to achieve amplification, thereby realizing the role of the switch.

[0037] Note that the above are only preferred embodiments of the present application and the technical principles used. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present application. Therefore, although the present application is described in more detail through the above embodiments, the present application is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. An audio amplifier circuit capable of automatically switching gain, characterized in that: include: A second amplifying module, a first amplifying module, a first input end, a second input end, and a second control end, wherein the first input end, the second input end, and the second control end are respectively used to receive a first audio signal, a second audio signal, and a second level signal; The second amplifying module comprises: a second amplifying unit, a first triode and a second triode; the negative input terminal of the second amplifying unit is connected to the drain or source of the first triode, and the positive input terminal is connected to the source or drain of the second triode; the gates of the first triode and the second triode are respectively connected to the second control terminal; the first input terminal is connected to the positive input terminal of the second amplifying unit; The first amplifying module includes a first amplifying unit, and a positive input terminal of the first amplifying unit is respectively connected to the second input terminal and an output terminal of the second amplifying unit.

2. The audio amplifier circuit capable of automatically switching gain according to claim 1, characterized in that: Also includes: Power module; The power supply module is used to output a working voltage for supplying power to the second amplifying module and the first amplifying module; Wherein, the source or drain of the first transistor receives the working voltage and is connected to the second control terminal.

3. The audio amplifier circuit capable of automatically switching gain according to claim 2, characterized in that: Also includes: External modules and MCU; The external module is used to output the first level signal and the second audio signal; The MCU is used for outputting a first audio signal, and generating and outputting a second level signal according to the first level signal.

4. The audio amplifier circuit capable of automatically switching gain according to claim 3, characterized in that: The external module includes a level output pin and a power access pin; The power supply access pin is used to access the working voltage; The level output pin is used to output a first level signal; When the external module is not connected to an external device, the level output pin and the power access pin are connected; When the external module is connected to an external device, the level output pin is disconnected from the power access pin.

5. The audio amplifier circuit capable of automatically switching gain according to any one of claims 1 to 4, characterized in that: Also includes: A first voltage dividing resistor; The first end of the first voltage-dividing resistor is connected to the first input end, The second end of the first voltage-dividing resistor is connected to the positive input end of the second amplifying unit.

6. The audio amplifier circuit capable of automatically switching gain according to claim 5, characterized in that: The first end of the first voltage-dividing resistor is connected to the drain or source of the first transistor; The second end of the first voltage-dividing resistor is connected to the source or drain of the second transistor.

7. The audio amplifier circuit capable of automatically switching gain according to claim 6, characterized in that: The drain or source of the second transistor is grounded, and the gate is connected to the drain or source.

8. The audio amplifier circuit capable of automatically switching gain according to claim 6, characterized in that: The first transistor is a P-channel MOS transistor; The second transistor is an N-channel MOS transistor.

9. The audio amplifier circuit capable of automatically switching gain according to claim 1, characterized in that: Also includes a first filtering unit and a second filtering unit; Two ends of the first filtering unit are connected to the negative input end and the output end of the first amplifying unit; Two ends of the second filtering unit are connected to the negative input end and the output end of the second amplifying unit.

10. The audio amplifier circuit capable of automatically switching gain according to claim 9, characterized in that: The first filtering unit includes a first resistor and a first capacitor connected in parallel; The second filtering unit includes a second resistor and a second capacitor connected in parallel.

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