Amplifier

Abstract

The invention relates to the field of circuit design and discloses an amplifier. The amplifier is provided with a slope voltage generating circuit, an enabling signal delay controlling circuit and an analog switch inside to enable the amplifier to realize lower circuit power consumption and low cost and reduce the impact noise during switching on or switching off, wherein the slope voltage generating circuit outputs a slope voltage signal to an operating positive signal input terminal when the external enabling signal is available; the voltage starts to rise from 0 V and reaches a reference voltage after passing T1, and then is continuously stabilized on the reference voltage; the enabling signal delay controlling circuit carries out the following operation when the input external enabling signal is available: changing the enabling signal which is output and connected with an operating enabling terminal into the available enabling signal, starting to operate, changing a switch controlling signal which is output and connected with a controlling terminal of the analog switch into the available switch controlling signal after delaying T2, and conducting the analog switch; and the analog switch conducts or cuts off the connection of an input impedance circuit and the operation under the control of the switch controlling signal.

Description

technical field [0001] The invention relates to the field of circuit design, in particular to an amplifier. Background technique [0002] Amplifiers are generally used to amplify or attenuate analog signals, filter, impedance transform, power drive, etc. For example, audio power amplifiers are used to amplify audio signals and drive speakers to produce sound. The coupling of the amplifier to the post-stage circuit or load (for the convenience of description, hereinafter collectively referred to as the load) usually adopts the following two methods: [0003] First, the direct DC coupling method. Such as figure 1 As shown, the operational amplifier 10 amplifies the input signal VI to output the signal Vo, and then inputs the output signal Vo to the load. In order to prevent the load from flowing through a DC current, an operational amplifier with the same power as the operational amplifier 10 is externally connected to the other end of the load. Amplifier 12. [0004] Alth...

AI Technical Summary

Problems solved by technology

[0009] When the operational amplifier 10 is turned on, that is, when the enable terminal EN of the operational amplifier 10 changes from a low level to a high level, the signal output terminal voltage of the operational amplifier 10 jumps from 0V to the reference voltage VREF very quickly (such as Figure 4 401 in ), and because the voltage difference across the DC blocking capacitor C1 cannot change suddenly, the voltage difference across the load will generate a positive spike with an amplitude as high as VREF (such as Figure 5 shown in 501), which is often referred to as boot impact noise, which will affect the user's experience and even affect the use of the device

For example, for audio processing equipment, the noise will appear as a loud "bang" from the speaker or earphones, causing unpleasant feelings to the audience, and may even burn the speakers or earphones

[0010] When the operational amplifier 10 is turned off, a similar situation also occurs, specifically, when the enable terminal EN of the operational amplifier 10 changes from a high level to a low level and the operational amplifier 10 is turned off, the signal output of the operational amplifier 10 The terminal voltage quickly jumps from the reference voltage VREF to 0V (such as Figure 4 402 in ), and since the voltage difference across the DC blocking capacitor C1 cannot change suddenly, the voltage difference across the load will generate a negative spike with an amplitude as high as VREF (such as Figure 5 shown in 502), which is often referred to as shutdown impact noise, which will also affect the user's experience and even affect the use of the device

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