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    Circuit don't work in Microcap (555-based class-D)

    Hello Maybe someone has simple (the simpler the better) circuit for a low-frequency transistor amplifier with a class D cascade, or can explain how to creat it, I'm going to make it in Microcap? I can only find very complex circuits in internet.

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    Re: Class D amplifier circuit how to make

    Run a 555 timer IC to generate a pulse train.
    Apply varying voltage to pin 5. This alters duty cycle.
    It's the makings of a class D amplifier.

    Click image for larger version. 

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    The LC network acts as a low-pass filter, second order. Its values need to be customized to the load and frequency.

    A load should always be connected so that the LC network does not start oscillating at its resonant frequency to an extent that becomes destructive.


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    Circuit don't work in Microcap (555-based class-D)

    Hello. I try to make first circuit from this article https://www.radiolocman.com/shem/sch...html?di=152208, but it doesn't work and I can't find what I miss, when make it in Microcap. Input frequence is 10000 Hz and ampletude is 5 V.

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    Re: Circuit don't work in Microcap (555-based class-D)

    Don't expect particularly good results from that circuit. In astable mode the control pin can change the frequency as much as the pulse width and the output is not AC coupled so it shouldn't be used directly to drive a loudspeaker or headphones.

    You will get better results if you trigger the 555 from an external fixed frequency and wire it in monostable mode. The 'out' connection should be connected to the load through a capacitor to remove the DC offset.

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    Re: Circuit don't work in Microcap (555-based class-D)

    Hi,

    ... or use a ready to buy class D amplifier IC.

    Farnell lists about 30 different ICs below 1€. And they have good audio quality and power.


    Klaus
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    Re: Circuit don't work in Microcap (555-based class-D)

    I cropped your schematic so it looks almost as clear as the original. I do not know why you changed all the R and C numbers.
    I think an old 555 timer makes a very poor class-D amplifier.



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    Re: Circuit don't work in Microcap (555-based class-D)

    The principle is to vary duty cycle of pulses (PWM) depending on voltage of input signal.

    Here is a class D amplifier, starting with a triangle wave generator (found in the Circuits menu of Falstad's simulator).

    Experiment until we discover which is a strategic spot where we can influence the triangle waves. Apply the incoming signal.
    Feed the output to a logic gate.

    Click image for larger version. 

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    Notice the carrier frequency itself does not change.



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    Re: Circuit don't work in Microcap (555-based class-D)

    Simpler yet. Start with an ordinary relaxation oscillator built from a single op amp. (Normal output is AC square wave.)

    Turn it into a class D amplifier by applying signal at strategic location.

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    I tried this in hardware and it works.



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