speech amplifier

[dr.power]

Hi guys,

Why the is using C2 and C4 feedback capacitor in this schematic which is a speech amplifier?
Why he wanted to double integrated from the input speech by adding the said caps?

Thanks

 

[Nigel Goodwin]

Hi guys,

Why the is using C2 and C4 feedback capacitor in this schematic which is a speech amplifier?
Why he wanted to double integrated from the input speech by adding the said caps?

Thanks

It's a VERY basic and simple circuit, the capacitors are to filter high frequencies.

I suggest you try learning about opamps and particularly opamp filters.

 

[dr.power]

It's a VERY basic and simple circuit, the capacitors are to filter high frequencies.

I suggest you try learning about opamps and particularly opamp filters.

Thanks Nigel
I know that an Integrator is a Low pass filter, But I am wondering why we need to use an integartor for a speech amplifier?
Why the designer wated to filter high frequencies? What kind of high frequency you talk about?

 

[Nigel Goodwin]

Thanks Nigel
I know that an Integrator is a Low pass filter, But I am wondering why we need to use an integartor for a speech amplifier?
Why the designer wated to filter high frequencies? What kind of high frequency you talk about?

All you want is speech frequencies, so you filter off the high frequencies and the low frequencies, this makes speech more intelligible, and reduces the bandwidth required - absolutely crucial for radio ham use, where narrow channel spacing is used.

 

[carbonzit]

I know that an Integrator is a Low pass filter, But I am wondering why we need to use an integartor for a speech amplifier?

Nigel has explained why one would want to filter high frequencies.

It might help your understanding to think of the capacitors as LPFs here, and not as integrators; that's not the function that's at work here.

 

[crutschow]

The resistor in parallel with the feedback capacitor makes it a low-pass filter with a -3dB rolloff frequency of 1/(2pi*RC). If there were no resistor than the circuit would be a pure integrator.