23 votes
Accepted

Is a minimum of 1000µF capacitance needed between an lm386's output and a speaker and if so why?

The capacitor referred in the video forms a high pass filter with the speaker (C-R filter). Its frequency response is given by the following formula: $$f_c = \frac1{2\pi \tau} = \frac1{2\pi RC}$$ ...
Wesley Lee's user avatar
  • 7,914
16 votes

LM386 amplifier circuit

Can anybody tell me why there is a resistor and capacitor in series at the output? It's called a Zobel network. The LM386 (just like its predecessor the LM380) doesn't like to run into anything like ...
Andy aka's user avatar
  • 457k
13 votes

What is the role of these capacitors?

This is not an op-amp, not even an approximation to one, it's a fixed gain power amplifier. That image is figure 16 from the TI datasheet for LM386. Unfortunately it only explains the function of cap ...
Neil_UK's user avatar
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12 votes
Accepted

(How) does LM386 allow an input past its negative rail?

Section 6.3 in the data sheet says that an acceptable input voltage is +/- 0.4 V. That is just below a single diode drop, so it would confirm your theory. Yes, that confirms what I thought about the ...
Andy aka's user avatar
  • 457k
11 votes
Accepted

How can LM386 follow a signal when it becomes negative?

Read the datasheet of the LM386: "The inputs are ground referenced while the output automatically biases to one-half the supply voltage." The chip adds an offset voltage internally. The way ...
Jonathan S.'s user avatar
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10 votes
Accepted

What is the purpose of the 250uF capacitor in the LM386 circuit?

Yes, 470uF will work fine, it will just extend the bass response somewhat. It's a coupling capacitor (or a blocking capacitor, to block DC, if you prefer). The 10R + 50nF is a "Zobel Network", ...
Spehro Pefhany's user avatar
10 votes
Accepted

LM386 gain-adjust bypass capacitor

Here the term "bypass" means "bypass for AC signal voltages. ie allow AC to pass without being affected by the resistor. LM386 data sheet here On page 3 they say: GAIN CONTROL To make the LM386 a ...
Russell McMahon's user avatar
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10 votes

(How) does LM386 allow an input past its negative rail?

Note: This answer and the one by Andy aka were posted independently and within minutes of each other. The content is virtually identical. I appreciate Andy's effort, so I accepted his answer. With ...
polwel's user avatar
  • 1,416
9 votes
Accepted

10W speaker with LM386?

You don't have a problem. You can connect a speaker that can handle 10W to an LM386 which can only output 1W. The speaker is rated 4 ohms which is compatible with the 4 ohm recommendation of the ...
Justme's user avatar
  • 149k
7 votes
Accepted

LM386 motorboating that goes away with a resistor in parallel with the bypass capacitor on pin 7

The main problem is that you have the gain of the LM386 set much too high. By putting a capacitor (C1) between pin 1 and 8 you have set the gain to 200 times. If the input signal is coming straight ...
Kevin White's user avatar
  • 33.2k
7 votes

LM386 amplifier circuit

When closed loop amplifiers drive a capacitive load, it can cause resonant gain peaks or even instability/oscillations. You can find a lot about this with the terms "opamp capacitive drive", ...
tobalt's user avatar
  • 22k
5 votes

What is the purpose of the 250uF capacitor in the LM386 circuit?

Figure 1. Typical LM386 amplifier circuit. For an audio application driving a loudspeaker alternating voltages must be generated. A positive voltage on the output drives the speaker cone one ...
Transistor's user avatar
  • 176k
5 votes
Accepted

What limits length of wire connecting audio amplifier to speaker?

The primary limiting factor will be the series resistance of the wire. Let us work with a speaker of 8 ohms. If the connecting wire were 18 AWG it has a resistance of 0.021 ohms per meter. If you ...
Michael Karas's user avatar
5 votes

Is a minimum of 1000µF capacitance needed between an lm386's output and a speaker and if so why?

Adding to Wesleys's great answer. It also depends on the size of the speaker. If it's little 2 or 3 inch speaker, it's bass output will already be severely attenuated so if you use a smaller ...
Trevor_G's user avatar
  • 46.7k
5 votes

What is the role of these capacitors?

Cap A does whatever the datasheet says about why you need to put it there. Or, if you don't always need it, the datasheet tells you what the purpose of pins 1 and 8 are. Cap B is for AC coupling the ...
Olin Lathrop's user avatar
5 votes

Volume control for LM386

You probably used a linear (B) taper pot. For audio you want an (A) log taper pot, so your 500 ohms will be about 25% of full electrical rotation, not 5%. Image from this site.
Spehro Pefhany's user avatar
5 votes

Why is the output signal of my amplifier heavily distorted?

Probably because the input signal level is too high. To test this, add a 100 ohm resistor from pin 3 to GND. The output volume will be reduced, but, if high input level is the problem, it also will ...
AnalogKid's user avatar
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4 votes

why do I get noise on the output of the LM386 when I connect speaker but not when I connect a resistor?

(1) Why could this be happening? Instability caused by inductance of the wiring and a possible 'ground loop' (ground wire shared between input and output signals). The circuit is oscillating because ...
Bruce Abbott's user avatar
  • 56.4k
4 votes

why do I get noise on the output of the LM386 when I connect speaker but not when I connect a resistor?

One aspect of the question: Why do we have the output connected to ground via a 0.05uF capacitor and a 10ohm resistor in most schematics in the datasheet? What purpose does this serve since this is ...
Kaz's user avatar
  • 20k
4 votes
Accepted

How to decrease distortion/noise of LM386 amplifier at max gain and volume?

After you updated the diagram: R4 is still in the wrong place. If you've built the circuit with R4 that way, then it is WRONG. With R4 where you have it, you lose a very large part of the volume. ...
JRE's user avatar
  • 71.4k
4 votes

How to decrease distortion/noise of LM386 amplifier at max gain and volume?

You have put R4 in the wrong place. You have put it in series with the loudspeaker which will waste more than 50% of the available output power. It should be in series with C6 down to ground (check ...
Steve G's user avatar
  • 5,305
4 votes

LM386 gain-adjust bypass capacitor

They make it sound like by adding this capacitor the resistor will be shorted but I don't see how this could happen. And that is exactly what happens here. A capacitor is like a short for an AC ...
Chupacabras's user avatar
  • 5,445
4 votes
Accepted

Ceramic capacitor value for an LM386N project

You have 10uF between pins 1 and 8. That sets the gain of the 386 to 200. 200 x 3.3 V = 660V. You are getting distortion because you are overdriving the 386. Work it backwards: You have a 4.7 V ...
JRE's user avatar
  • 71.4k
4 votes

LM386 speaker distorts

Compare your circuit with an example from the datasheet: You have the + input grounded rather than the - input as in the datasheet. The LM386 only works properly when the - is grounded and signal ...
JRE's user avatar
  • 71.4k
4 votes

simple LM386 amplifier noise

The simplest way to fix your circuit is to build it as the datasheet recommends: Notice the variable resistor connected to pin 3. You describe the problem as "noise when the music is playing," which ...
JRE's user avatar
  • 71.4k
4 votes

simple LM386 amplifier noise

The LM386 has two inputs; they are differential like so: - Ignoring the ridiculous value of the input capacitor on pin 2 in your picture, you basically have both inputs fed from the same signal and ...
Andy aka's user avatar
  • 457k
4 votes
Accepted

LM386 LTspice simulation output problem

Input voltage range is too high. Limit is +/- 0.4V.
Justme's user avatar
  • 149k
4 votes

LM386 circuit design questions

First problem is that usually a PP3/LR61 type 9V battery can't provide enough current to power the amplifier to drive an 8 ohm speaker. Otherwise the component values are pretty sane, except for the ...
Justme's user avatar
  • 149k

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