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question about low power audio amplifier circuit

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riceboy89

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hey

regarding this circuit (**broken link removed**)

is the resistor on the left simply a 10k potintiometer? i just found it odd the way the pins were hooked up. could you also explain what this resistor will allow me to do? adjust gain?
 

do you mean this website? **broken link removed** (note the 386 instead of 368)

yes that is just a pot. It is there to serve as adjustable attenuation before the gain of the opamp (possibly to prevent saturation)

honestly, i don't much like the circuit as better audio amps can be built w/ just a few more component and feedback. but it is, as the site advertise, extremely simple.
 

It is just for volume adjustment by adjusting the input signal level of the IC, and must be B-type potentiometer.

nguyennam
 

whats the difference between a regular pot and a b-type pot?

also, i am making a radio so is the more gain i have, the better? also would a gain of 200x be good for a small one transistor radio?
 

Basically and popularly, there are 2 types of potentiometers: A-type and B-type.

A-type, or linear type: resistance portion of pot. is directly proportional to the rotation angle of the pointer. This type is used in any place when need linear, for example: equalizer/treble/bass adjustment in audio amplifiers.

B-type, or logirithm type: resistance portion and rotation angle have a logarithm relation. This type is used mainly in volume adjustment in audio amplifiers.

These types are shown in pot. values on packages, for example: 10kA, or 10kB, means pot of 10kiloohm of A-, or B-type.

In principle, we expect higher gain in any amplifier. But higher gain makes system become more unstable. 200x gain may be good enough for your project, and you can easily adjust its value at IC amplifier to get your best result.

For LM386, you should look for the datasheet from National Semiconductor, as this is the original manufacturer, and NS often provide very detailed information for application in their datasheet, as well as seperate application note for the IC.

nguyennam
 

regarding the scmematic, the one given above does not have a bypass capacitor. on the spec sheet, they show an amplifier circuit and that one has a bypass cap off of pin #7 then going to ground. should i include this capacitor, or should i use the schematic above?

also, on the circuit in post #2, the only pot i need is the 10k one on the left right? my electronics teacher said something about a variable capacitor because that circuit given is only good for 20x gain.

thank you guys immensly for answering my questions.
 

bypass cap is just to quell potential oscillations from the DC power supply, its good practice to put a .1uf cap from vdd to ground whenever prototyping something like this. in terms of gain, really feedback is a better idea for something like this to achieve higher gain and stability, running a op-amp open loop really causes it to act like a comparator with bad slew.
 

    riceboy89

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umm sorry if i sound dumb, but i only got the .1uF part. :|

but is it totally necessary to add this? im trying to minimize parts seeing im a broke high school student.



here is what i have so far

**broken link removed**

-multisim didnt have some of the components i needed (such as a .005uF cap) so i just put in a resistor for it.

-the 8 pin chip is the audio amplifier.

-j1 is a coil which i will make

-j3 is the TL431AIZ voltage control zener

-j5 is the headphone jack

-j7 is the speaker output

another question. should i ground the gate or case lead on the 2N4416 jfet transistor?

and finally, where can i add an l.e.d indicating power? i obviously cant feed an l.e.d 9v without it crapping out on me.

thanks much
 

regarding the scmematic, the one given above does not have a bypass capacitor. on the spec sheet, they show an amplifier circuit and that one has a bypass cap off of pin #7 then going to ground. should i include this capacitor, or should i use the schematic above?
but visit the below site



http://www.atmel.com/dyn/resources/prod_documents/doc4655.pdf
 

ok ill include the bypass cap for good measure then.

everything else look ok?

plz help answer the above questions. my deadline for this project is nearing.
 

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