| Lazer |
Made this simple subwoofer amplifier based on the mj15024 and mj15025. But after som playing the r4 burns and the opamp turns to ****.
Cant see why this is happening!!
Some suggestions?
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| Netlist |
Are the values of the resistors on the drawing the actual ones?
I think it's a bit strange that you can even get sound out of this schematic. Simulations gives very strange results. We need some opamp gurus here.
/Hugo :) |
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| pinkmouse |
I agree, R1 and R2 seem very high
Surely C1 should also be directly in the output of the op amp, you are feeding the bias from the top transistor straight back into the chip.
Is the voltage divider set up by R3 and R4 supposed to reduce the output swing to what the chip can handle as feedback?
I am not a great electronics guru, and this circuit confuses me greatly. |
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| zagisrule! |
Hehehe...
You have some major issues with that circuit buddy.
Problem #1: What is the 1uF doing there? My guess is that you want it to pass audio to the bases of the BJT's? If so you need two of them. And if you want any bass out of the thing you need to up capacitance to at least 100uF, 200+ being more reasonable especially considering this is a sub amp.
Problem #2: Your emitter resistors are way too big! 1 ohm or less to encourage load sharing (when using multiple BJT's in parallel - in this case you don't even really need them).
Problem #3: Your feedback circuit is way out of whack, the lower resistor need to have a much lower value. The gain the way it is is over 100 and that is not feasable unless your input level is extremely low. Try making R4 1K or so for a gain of 11.
Problem #4: If you want to utilize a DC servo for output offset correction you will need to add resistors from the output of the op-amp to the bases of the BJT's to allow a DC current path for the op-amp to adjust the bias and keep offset managable.
I have attached a modified circuit diagram to try that should keep you from blowing things up! :)
The caps and resistors I added are flexible as far as values go, maybe 1K or so for the DC servo resistors, and anything over 200uF for those caps.
-Matt |
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| sivan_and |
| My suggestions....:D |
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| zagisrule! |
I wouldn't go much under 10K.
You might also want to add compensation capacitors.
-Matt |
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| Carondimonio |
Maybe I' m stupid, but it seems to me that the lower Transistor is REVERSED!
Cheers,
Bruno |
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| GregoryD |
Well there are multiple problems with the schematic as shown:
1. The MJ15025 is drawn/installed incorrectly. The collector needs to connect to the -V rail. The emitter connects to R2.
2. As already stated, R1 and R2 surely cannot be 10K ohms. These are typically less than 1 ohm.
3. Make sure there is some resistor (about 50K) installed from pin 3 of the op-amp to ground.
4. The gain of the op-amp circuit is set to 101... this is really high, maybe change R4 to around 470 ohms.
5. Consider adding a capacitor in series with R4 if a high-offset voltage op-amp is being used.
6. Consider a small capacitor around R3 to help supress any oscillations that may become evident when you get this thing working.
7. As already stated, the wire going from pin 1 of the op-amp to the base of the MJ15024 needs to be removed and replaced with another capacitor just like C1. This will allow the bias circuitry to work properly. C1 and the new capacitor that you add need to be higher in value... about 100 times higher.
Good Luck!
GregoryD |
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| GregoryD |
Also... make sure that the op-amp you are using is capable of the high supply voltages. It needs to be rated for +-18V operation. Check your P.S. voltages and make sure they don't exceed the max. ratings of the op-amp. You may need to lower the values of R5 and R6 after you get the circuit working to bias the output devices correctly.
Later,
GregoryD |
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| Lazer |
| Oops i can see that i did som major errors when drawing this circuit. Infact the resistors r1 and r2 are 0,5 ohms and the transistor is definetly drawed in the wrong way |
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| janneman |
| quote: | Originally posted by GregoryD
[snip] 7. As already stated, the wire going from pin 1 of the op-amp to the base of the MJ15024 needs to be removed and replaced with another capacitor just like C1. This will allow the bias circuitry to work properly. C1 and the new capacitor that you add need to be higher in value... about 100 times higher.
Good Luck!
GregoryD |
There is nothing wrong with the connection of the opamp output to one of the output bases. With the feedback down to DC, the opamp will take care of the offset: the opamp output will be whatever it needs to be to have a zero output voltage. The 470uF for C1 is overkill: since the bias circuit can be considered a voltage source, the cap is not needed at all. A cap in parallel of a voltage source doesn't do diddly.
But I agree that the gain was too high, and you need a resistor from the non-inverting input to gnd, 10k would be fine.
BTW, on most opamps pin 6 is the output, not pin 1. Are you sure that connection is OK?
Jan Didden |
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| Workhorse |
| quote: | Originally posted by janneman
There is nothing wrong with the connection of the opamp output to one of the output bases. With the feedback down to DC, the opamp will take care of the offset: the opamp output will be whatever it needs to be to have a zero output voltage. The 470uF for C1 is overkill: since the bias circuit can be considered a voltage source, the cap is not needed at all. A cap in parallel of a voltage source doesn't do diddly.
But I agree that the gain was too high, and you need a resistor from the non-inverting input to gnd, 10k would be fine.
BTW, on most opamps pin 6 is the output, not pin 1. Are you sure that connection is OK?
Jan Didden |
Hi Jan-Didden,
Absolute confirmation of Gentleman indeed.;)
Agree with you a lot, in this case only.:D
cheers,
kanwar |
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| janneman |
... and normally pin 7 is pos supply, not pin 8....
Jan Didden |
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| Tube_Dude |
| quote: | Originally posted by janneman
The 470uF for C1 is overkill: since the bias circuit can be considered a voltage source, the cap is not needed at all. A cap in parallel of a voltage source doesn't do diddly. |
Hi Janneman
In this circuit the cap is crucial , because the op amp can't sink current from the the lower output transistor.
The op amp try to drive a the lower transistor but the string of the diodes don't let current to pass in reverse mode.
The only path to sink current from the lower transistor is R6 that is 10 k and can only sink ~ 2mA maximum (not enough for a output transistor.)
Is the discharging current from the capacitor , that must be of high value, that drives de lower transistor. |
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| mod_evil |
Hi!
Can I use TIP141 and 145? It's more inexpensive... What the difference of sound? How much ampers the amp use...? |
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| Lazer |
Wired it up now and it works fine
Thanks for all help
The opamp pin config: It is a dual in one opamp causing the leg config to be somwhere different. |
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| Tube_Dude |
| quote: | Originally posted by Lazer
Wired it up now and it works fine
Thanks for all help |
If you instead of a regular transistor (MJ15025 /24) used a darlington complementary pair , you will get a much improved performance. |
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| Tube_Dude |
| quote: | Originally posted by mod_evil
Hi!
Can I use TIP141 and 145? It's more inexpensive... What the difference of sound? How much ampers the amp use...? |
Yes you can, and with much improved performance , because TIP 141 / 145 are Darlington transistors.
But you must use two more diodes, in the bias string.
Aquele abraço! |
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| Upupa Epops |
| To Jorge : Yes, he get improved parametres, but lower power and worse thermal stability. Can we call this amp as " subwoofer amp ", if output power will be cca 10 W/4 ohm ? It will be not Tyranosaurus's steps, but steps of lizzard ;) . |
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| janneman |
| quote: | Originally posted by Tube_Dude
Hi Janneman
In this circuit the cap is crucial , because the op amp can't sink current from the the lower output transistor.
The op amp try to drive a the lower transistor but the string of the diodes don't let current to pass in reverse mode.
The only path to sink current from the lower transistor is R6 that is 10 k and can only sink ~ 2mA maximum (not enough for a output transistor.)
Is the discharging current from the capacitor , that must be of high value, that drives de lower transistor. |
Yes you are right. Often you see at least a double, or even a triple at the output, darlinton-wise, and then the standing current from the bias is enough to drive the output either way, and the opamp merely needs to move the voltage around. That is how I normally do it, but you are absolutely correct, because of the single output device used here the opamp has to drive that base.
Which means the cap is required. Which brings another question: can the opamp drive sufficient base current to let the output stage drive a speaker? What's the beta of those output devices, 40, worst case, or even less? So, at 4A peak output current the opamp needs to source 100mA peak. Tough.
Jan Didden |
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| Tube_Dude |
| quote: | Originally posted by janneman
Which means the cap is required. Which brings another question: can the opamp drive sufficient base current to let the output stage drive a speaker? What's the beta of those output devices, 40, worst case, or even less? So, at 4A peak output current the opamp needs to source 100mA peak. Tough.
Jan Didden |
Yes ...you are right! ;)
For a beta of 40 in the output transistors ,the op amp will need to drive 4 Ohms X40 = 160 Ohms.
The humble LM358 can't drive 160 ohms without heavy distortion...
How can this amp sound good??...:eek: |
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| Tube_Dude |
| quote: | Originally posted by Upupa Epops
To Jorge : Yes, he get improved parametres, but lower power . |
No ...the output power will be greater with the darlington , because the LM 358 with his 20 mA output current can't drive the output transistors for a full swing in a 4 Ohms load . |
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| Upupa Epops |
| Fullswing will be theoreticaly lower with darlingtons, but all this solution is wrong :cool: . Theoretical best results give only diamond structucture, but it is quite different legue ;) . |
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| bobo1on1 |
| Why are you using 3 diodes to bias 2 transistors? Idle current will be huge. |
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| burnedfingers |
Altec Lansing uses a 5532 op amp to drive the output stage in their 9444's and 9446's. EV is the same amp with its 2600 and 3200 model.
I recommend derating the rail from +- 18volt to +- 15volt for the op amp to keep it alive for a few years longer. I realize the op amp is rated for +-18volt but doesn't last very long. |
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| burnedfingers |
Quote:
Why are you using 3 diodes to bias 2 transistors? Idle current will be huge.
Unit will also double as a space heater if and when all the bugs are out of it. |
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| janneman |
| quote: | Originally posted by bobo1on1
Why are you using 3 diodes to bias 2 transistors? Idle current will be huge. |
With the .5 ohms Re's Iq will be around half an amp. High for an AB, but not really huge, I think.
Jan Didden |
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| GregoryD |
janneman you are correct! Ignore item #7 in my previous post, it was wrong. In fact, you need a DC path to the output to maintain the operating point.
Later,
GregoryD |
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| mod_evil |
| quote: | Originally posted by Tube_Dude
If you instead of a regular transistor (MJ15025 /24) used a darlington complementary pair , you will get a much improved performance. |
Para você também
For you also.
I found the TIP41 and TIP42 in my case. I can use the tips in this amplifier? What the rms this amplifier make?
I analyse the amplifier, and decide use one capacitor ( 4700uf x 50v ) in sequence of the output...
Tanks for your reply. |
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| Tube_Dude |
| quote: | Originally posted by mod_evil
I found the TIP41 and TIP42 in my case. I can use the tips in this amplifier? |
I have already told you yes , in my post #19.
| quote: | | What the rms this amplifier make? |
With the Tip and with 18 volts rails, approximately 15 W in 8 Ohms. |
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| Upupa Epops |
| To Jorge : LM 358 have max. rail voltage +/- 16 V max. , voltage swing 28 V pp, with darlington output cca 25 V pp. , which is cca 9 V RMS = cca 10 W/8 Ohm, practicaly less ( cca 7- 8 W ). It is realy strong amp for sub :D . |
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| demogorgon |
Now, Lazer, this is a amp i find myself really wanting to see!
how about sharing a pic of it?
-marius |
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| bobo1on1 |
| quote: | Originally posted by janneman
With the .5 ohms Re's Iq will be around half an amp. High for an AB, but not really huge, I think.
Jan Didden |
Actually it will be around 900 mA if the diodes are not on the heatsink, that consumes more than 30 watts at idle.
Anyway 2 diodes works just as well, there is absolutely no need for 3 diodes. |
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| mod_evil |
| quote: |
I have already told you yes , in my post #19.
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In the post #19 you confirm the yes for TIP141 and 145 in now i want to yes in the tips41 and 42
Tanks |
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| Tube_Dude |
| quote: | Originally posted by mod_evil
In the post #19 you confirm the yes for TIP141 and 145 in now i want to yes in the tips41 and 42
Tanks |
It seems that nobody here like to do the home work...yes...you can use the TIP 41 /42... |
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| Tube_Dude |
| quote: | Originally posted by Upupa Epops
To Jorge : LM 358 have max. rail voltage +/- 16 V max. , voltage swing 28 V pp |
Obviously the NE5532 is a better option here , because it can work with +- 22 volts rails. |
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| destroyer X |
And mixed in the middle of those highly valuable persons, you!, my friend M_evil.
Dear Felipe, my friend that born in my wonderfull town, Rio de Janeiro City.
The place where Nature made a marriage with the Gods!
Felipe, Epupa have visited the thread you are many times, this is enormous honor, he is one of the 10 best wide world amplifier designers, wasting patience(and time too)
with us.
The Man, the one with multiple capabilities.
Janneman, the Count of Luxembourg, having deep Psychology knowledge and sciences too... outstanding intelligent man.
Laser contributing this way, other honor, he do not enter all the time.... a rare oportunity.
Bobo1 to 1, the one that can call himself as bobo, have deep knowledge of mankind...he see the true and smile of that, this is menthal health, artist, with enormous intelligence, and do not waste words to talk everywhere alike a parrot (me)
Tube Dude, a sacred monster of experience.... this guy have half century of knowledge applied into electronics
Zagisrule is a brilliante man...have his own ligth...watch his entrances on forum and you will see that.
Carondimono, the Macarroni, full of happyness and life
Sivan is the one that has many values, images, sound and science deep interest and culture
Workhorse!...do you know this man....is he contributing?...this man is an industrial, constructor of professional wonderfull amplifiers...advance audio designs, a simple, and famous man!
Netlist know human spirit, our of normal, enormous sensitivity man...when we are starting some thinking, he already finished to realise and have solution..impressive person.
Gregory D, have deep consistence wherever he talks.
And the member of the Royalty, Pinkmouse, someone that i understand as "A lover on earth", the mankind lover, have feelings and passion, understand deep people feelings, having sense of humor and tollerance.
Your are in the middle of wonderfull people...i suggest you friend Felipe, to open a big smile, as you are beeing received, in this thread by astounding people.
If you have the luck to be together SY, Hugh Dean, Eva, MikeB, Mateus and more 14 golden minds.... i will very proud of you...ans will be with you as you are lucky!
Congratulations Felipe M_evil.
Carlos |
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| Upupa Epops |
| Carlos, you are realy poet ;) , spring is coming :cool: - och pardon, I forget that on south coming autumn :xeye: . Or some drink ? :clown: |
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| destroyer X |
Here is always hot...all year 29 degrees centigrades when you are near the beach.
Winds is always blowing from the sea.
We are warm inside, alike our environment..... we are feelings as the main characteristic...peacefull as the second characteristic, tollerance as the third, and innocent as the fourth...brazilians are this way...of course...there are differences here...we have all world inside this country...all them mixed.
Have not shame to talk of feelings.... this is free here...there are many things free here....friends are free...girls too.
regards,
Carlos |
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| destroyer X |
I will be laughing as a hell because your beer moustache.
that's me!
Carlos |
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| mod_evil |
The topic amp with my modifications...
what you think?
The resistence of the bias ressitor is correct?
Tanks for attention |
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| Tube_Dude |
| quote: | Originally posted by mod_evil
The topic amp with my modifications...
what you think? |
That you haven't pay attention in what we have told you in this thread.
1- The Lm 358 can't work with more than +- 16 volts rails.
2-If you use a triple follower , you must not use Darlington transistors , but "regular " ones.
3- If you use a dual supply (+- rail voltage ) the output capacitor is not needed .
4-The emitters resistors of the output transistor must be 0,5 Ohms or less.
5 - You must use more biasing diodes ( one for each output transistor) and a pot for regulation of the output stage bias.
6- The resistors marked * must be ~ 10 k Ohms each.
Ufa!...;) |
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| mod_evil |
| quote: | Originally posted by Tube_Dude
That you haven't pay attention in what we have told you in this thread.
1- The Lm 358 can't work with more than +- 16 volts rails.
2-If you use a triple follower , you must not use Darlington transistors , but "regular " ones.
3- If you use a dual supply (+- rail voltage ) the output capacitor is not needed .
4-The emitters resistors of the output transistor must be 0,5 Ohms or less.
5 - You must use more biasing diodes ( one for each output transistor) and a pot for regulation of the output stage bias.
6- The resistors marked * must be ~ 10 k Ohms each.
Ufa!...;) |
hohoho...
1 - The 30+- is the one mistake...
2 - Why i not use the darlignton transistors?
3 - Ok
4 - What the funcion of the emmiters resistors?
5 - I prefer one resistor, its simple.
6 - Ok, i use the 100ohm or 10k ?
Thanks. |
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| zagisrule! |
Not to mention that the LM358 has a class B output stage and you will get NO sound quality from it whatsoever.
Why use a triple follower? There is no reason to use it for something like this, essentially a waste of a transistor pair. Double follower would be more than adequate to drive a few output transistors if you find the need to drive a low impedance load.
Use above 5K or so with those biasing resistors or you will have a major heat source on your hands. Like tube_dude reccomends 10K is a good place to start.
Also, if you expect the op-amp to correct for DC offset issues you will also need to add a DC voltage path from the output of the op-amp to the first set of ouput transistors. Without them the amplfier output stage is AC coupled to the VA and therefore DC offset will build in the ouput stage and the op-amp will have no way to correct it. Try 1K resistors as a start here.
BTW: I believe it is the OP445 high-voltage op-amp that permits 70V across the +/- terminals therefore allowing operation on +/- 35V rails, or +/- 30V if you like to stay conservative.
-Matt |
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| mod_evil |
| quote: | Originally posted by zagisrule!
Not to mention that the LM358 has a class B output stage and you will get NO sound quality from it whatsoever.
Why use a triple follower? There is no reason to use it for something like this, essentially a waste of a transistor pair. Double follower would be more than adequate to drive a few output transistors if you find the need to drive a low impedance load.
Use above 5K or so with those biasing resistors or you will have a major heat source on your hands. Like tube_dude reccomends 10K is a good place to start.
Also, if you expect the op-amp to correct for DC offset issues you will also need to add a DC voltage path from the output of the op-amp to the first set of ouput transistors. Without them the amplfier output stage is AC coupled to the VA and therefore DC offset will build in the ouput stage and the op-amp will have no way to correct it. Try 1K resistors as a start here.
-Matt |
Hmmm why my triple stage of exit signal is incorrect? |
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| zagisrule! |
It is just not necessary...it would work but why bother with it in this case?
Not incorrect but not the most straight-forward.
"Everything should be as simple as it needs to be, but no simpler" - Einstein (I think??)
-Matt |
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| mod_evil |
I understand...
The frist schematic in the post is the correct? This is work?
/mod |
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| destroyer X |
The first schematic is more adequated, as use the supply voltage correct to not burn the Operational Amplifier, the Op amp.
This one has not too much power in it's output, different from those 10 watts TDA chips.
It produces voltage swing but cannot be connected to low resistance, as speakers, because voltage will go down and chip will burn by excess of current.
So, those 18 volts is very good, not only to the chip, but also to the output transistors.
Those output transistors will be current amplifiers with no voltage gain, in other words, they will produce big current with the excite voltage that will came from the op amp.... the op amp output voltage will appear at the output, but together with the capacity to be developed over low resistance as speakers.... and voltage together current is power.
Your emitter resistor must be small, not to absorb the current, they must be a low resistance way to colector to emitter current, because this current will cross the speaker.
In the positive cicle of some wave, the upper transistor will conduct and energy will pass inside its colector, will continue travelling from its emitter, will cross speaker, the speaker will move forward because of that, and the energy will be sent to ground.
In the negative cicle, things turn inverted, now the lower transistor will conduct, will have low resistance and energy will go passing inside.
The upper transistor need 0,6 volts of bias voltage, use a single transistor, or two TIP41 to the up side and TIP42 to the negative side.... 2 diodes in series may be enougth, as each one of them keep, as a zener diode, 0.6 volts over its terminals.... to increase a little, if needed, put in series with those 2 diodes, one 100 ohms trimpot to increase bias voltage if needed, but start with the zero ohm position as a standard adjustment.
Using simetrical supply, you will have low dc voltage in the output terminal...some milivolts that can travel inside the speaker coil without terrible problems, this is called off set voltage.
Those output transistor will have some current flowing, as operating in class AB they will have more than 550 milivolts measured from base to emitter, and colector to emitter circuit will be conducting some miliamperes, that current will be stand by current, result of biasing, and bias or biasing, or quiescent current point is the result of how big is the base to emitter voltage..... 550 milivolts will produce small current.... 600 milivolts will produce big current....650 milivolts will produce enormous colector to emitter current that may "kill" the transistor... this current flowing produce heat, and is a need waste of energy...some heat will be there, alike an automobile engine, turning iddle, 900 rpm, only working, stopped, in stand by mode, ready to start to move will produce heat without any movement...just to be ready....in stand by mode, to start to run.
That current, in small amplifier can be lower as 5 miliamperes each transistor..... can be higher, alike 50 miliampéres each transistor, and when drive into class A, can be very big, as 1 ampere of more....and many watts of heat is produced there, as the result of current flowing inside transistor that is presenting some resistance to electrons flow...... resistance and current produce heat!
Your case, some miliamperes may be OK!...this is class B operation.
You do not need to put bigger voltage than 18 volts.... i do not know the voltage swing, the maximum voltage swing of this op amp, but seems to be more than adequated to use the same 18 volts to the output transistors....first to avoid burn the chip, and second because the voltage swing may not exceed the maximum voltage you have.... 18 positive and 18 negative, result in 36 volts peak to peak swing maximum...this is something alike 12 volts over 4 ohms speaker.....35 maximum RMS watts...but in reality will not be so strong this way....will need two transistor pairs, as those transistors you wanna use can dissipate 60 watts of heat each one....but this is not reality.... not more than 30 watts of heat each one...this way you will have a over dimensioned output using two pairs...more safe to you.... 200 squared centimeters of aluminium will be enougth to dissipate the heat..... 200 square centimeters to each half cicle..... one plate to the upper 2 TIP41 and another plate to the lower 2 TIP42.
That Electra School you have studied loose quality those early years..... i studied there, my father also, and also the father of my father..... but those informs they fail not to give to you...their fault...they are failing (pisando na bola legal mesmo com você), they are failing with you hardly.
I suggest you to read entire forum, and use my person, in direct mail, for a while, waiting more experience, those guys that helped you are advanced related you knowledge, and beeing highly patience with you...very kind guys, Mr. Evil is a teenager, a very good person, starting electronics and you all very kind.
You do not need the electrolitic condenser in the output, as it is used when you have DC voltage that can cross speaker and burn it...in your case, with simetrical supplies, you will not have so big voltage there.... and if you find big voltage there....some error must exist.... this is not the expectation.
The first schematic may work, some development can be done, some better bias adjustment and tweak here or there...but may work very well.
Yes, you can use darlington if you want it, but we need to increase the diodes to four units, because darlington needs more bias voltage from base to emitter, they are the same as two transistors inside same case, and have some auxiliary resistors too, and one diode to protection also....beeing two transistors...0.6 volts from base to emitter will be not enougth, they will not conduct, and if you force them to work this way they will distort as a hell, because the audio will make it work somethimes and switch off other times....aaaaagh!..will be terrible to your years!
Use two diodes to each darlington...0,6 plus 0,6 volts will be good to each one of the two transistors that are inside the darlington transistor....or darlington chip if you prefer...a chip with three terminals...so four diodes.... and will be more sensitive, and will reach more power, and will distort more also....better to keep the standard design published....and measuring the standard design, you can change a little here or there to be satisfied with your personal touch on it.
The output electrolitic, is used to block DC current, it let the alternated current (audio) cross it...you do not need it in this circuit.
You can use 2 supplies, one with plus 18 and minus 18, because of the chip amplifier...and can use another higher one to output...but in the reality will give you nothing...no advantage to put 30 or 40 volts there, as that voltage will never be used to the output audio swing....the swing depends on the voltage amplifier...the chip in your case...and it will not produce voltage enougth to a bigger voltage swing...so.... not needed.
As a comparison....it is the same as use a 400 hundred horsepower automobile engine...and be forced by law to go 20 miles an hour....waste of power.
fica só lendo por enquanto, Electra está muito fraca pro nível da turma daqui do forum.
regards
Carlos |
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| destroyer X |
I think this point is reasonable.... a real check and a real work.
those developments that you could see after...can be good of course...but need a little bit of work on them and more skilled constructors.
And for a beginner, when the thread openner said OK!, and accepted as good....may be good enougth Because assembled and heard, beeing considered good.
this is a message directed to my personal friend Felipe.
Our forum guys, in a big majority are all scientist...they are always improoving something...never finish.... a never ending history...and a never ending amplifier too.
Accept the thread opener point of view, to finish this amplifier and jump to another one to get more and more experience.
And thanks all forum guys, you gave a precious support to my friend.
regards,
Carlos |
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| teemuk |
There seems to be an "error" in mod_evil's modified schematic. TIP142 is NPN and tip 147 is PNP. The schematic is drawn correctly but i think you mistakenly named the transistors in your schema. Also, TIP142 is complementary pair to TIP147 so why use TIP141?
Teemu K |
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| alan brando |
here there is your amp idea with a few modifications.
as you can see, I've replaced the diodes for a transistor to improve bias/temp adjustment, and depending of which class do you want to use, you can change the R3 & R4.
One of the reason of your problem is that you omitted C4 & R14 at the amp out and the other is you also omitted R1 & R2.
If you replace the BJT transistors for Mosfets, the circuits will be better and you don't need to change the circuit.
Use a 5534 for the opamp.
cheers! |
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| Lazer |
Thanks for all help.
My old design (with proposed mods) is currently working well as an subwoofer circuit.
Regarding the last proposed circuit i will try to build another amplifier with this. |
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| burnedfingers |
alan brando
Do you have a better picture? All I get is a black screen. |
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| alan brando |
| I've inverted the background colour, I hope that you can see the circuit now, if you can't, please contact me I'll try with a different software. |
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