so added Vcc to the amplifiers won't affect their gain?
No it won't.
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so added Vcc to the amplifiers won't affect their gain?
http://hackaweek.com/hacks/?p=327 cant i use a model like this? i just have to adjust the gain to 20, it uses a 9v supply too.
I'll tell you now, if Mozart had had access to electric guitars, all the effects, amps and digital recording etc he would not have wasted another minute plunking away on that silly piano!
The reason all your beloved classical music is full of pianos and violins etc is because the great composers of the day simply did not have any better instruments! The great composers of today DO.
don't know about that, a guy i used to work with listened to a heavy metal band that used violins, cellos, etc and it sounded just as crunchy as a guitar with the amps that go to 11
Fourier components of V(out)
DC component:0.041857
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 3.074e-01 1.000e+00 -0.10° 0.00°
2 2.000e+03 8.688e-04 2.827e-03 75.19° 75.29°
3 3.000e+03 6.633e-04 2.158e-03 -122.11° -122.01°
4 4.000e+03 2.622e-04 8.531e-04 15.66° 15.76°
5 5.000e+03 5.618e-04 1.828e-03 -127.37° -127.27°
6 6.000e+03 4.788e-04 1.558e-03 -25.77° -25.66°
7 7.000e+03 2.848e-04 9.264e-04 -122.90° -122.79°
8 8.000e+03 5.749e-04 1.870e-03 -24.35° -24.24°
9 9.000e+03 2.175e-04 7.076e-04 -126.94° -126.84°
Total Harmonic Distortion: 0.489885%
not too bad for a "quickie" amp....
maybe he's just frantically building and testing to make his deadline....
so i played with the first amp circuit i posted and did some of the "tweaking" to see if it would work off +/- 4,5V. the reason i did that is it does take some radical tweaking to get the constant current sources to properly bias the diff amp and voltage amp stage. i purposely did not add the bias diodes for the output transistors because i wanted to illustrate something for the OP. this circuit operates pretty much like an op amp you get in a chip, but it's capable of several watts instead of a few milliwatts. the crossover notch is barely visible in the output waveform, because like an op amp will do whatever it takes for the inverting (base of Q2) input to be equal to the noninverting input (base of Q1). you can see what action takes place to make this happen. there are spikes in the current through Q7 to make Q7 slew through the crossover region, with the result being most of the crossover notch distortion is removed. you can also see this in the near vertical transitions in the voltage at the bases of Q5 and Q6. the crossover notch distortion could be completely removed by adding bias diodes between the bases of Q5 and Q6, but because of the feedback action, you can see that the actual distortion at the zero crossing is very small. i didn't want to do the OP's work for him, but i figured he could learn something about how amplifiers work, that most people have a hard time understanding.
so the first picture shows the tweaked amp and in green, the output waveform, in blue, the emitter current through Q7. and in red the base voltage of Q5 and Q6. the second picture shows a closeup of the same 3 waveforms and the action of the feedback to minimize the crossover notch distortion.
Here is a VERY SIMPLE class-AB power amplifier that is powered from an ordinary 9V battery.
It produces 0.8W into an 8 ohm speaker with fairly low distortion.
Its little output transistors will probably survive playing anything for a long time.
may i ask a question if you may, where did the 8.5 v came from? did the 1.3 v from "8.5 - 1.3 v = 7.2 v" came from the two diodes? and also how did you arrive at such values of resistor? please teach me how.
also why is the 8 ohm load connected to the supply dc voltage? i thought the speaker does not need a dc supply?
We were TAUGHT about electronics. It looks like you were not taught about electronics.im constantly amazed by how easy for you to design something like that, but how did you arrived with the values of resistors? cause that is my main problem with my design, i have to defend it and explain why i used that or those particular resistors.
I showed that the maximum undistorted output voltage swing is from 1.3V to 8.5V. I increased the input signal level here to show when the output is clipping with severe distortion then the output signal swing is a little more from 1.1V to 8.6V but you NEVER measure a distorting amplifier.where did the 8.5v come from? where did the 1.3v come from?
The speaker and the output coupling capacitor C3 BOOTSTRAPS the base current for the NPN output transistor for a higher output signal swing. You need to learn about amplifier bootstrapping (ask your teacher or look in Google).why is the 8 ohm load connected to the supply dc voltage?
No.did the 1.3 v from "8.5 - 1.3 v = 7.2 v" came from the two diodes?