can't see an amp circuit on page 16. can you give the post number?
Thanks, what softwave did you use?
Thanks, what softwave did you use?
I am start to learn use Eagle for a few weeks, almost I know nothing even can't draw a resistor, may I am a foolish child?
.But R19 and C11 still without values. I will change TIP41-42 with TIP35-36.
Surprise, I not fail the exam, too lucky, the mark is higher than what I calculated
Excellent about the exam results- you had jumped the gun.
Yeah, TIP41C-42C (2000VND) much cheaper than 35C-36C (11000VND). I don't like to use A1015-C1815 and A1013-C2383 because many of them are Chinese clone, I think TIP41C-42C will be much better than A1013-C2383, BC337-327 or BC550-560 will be better than A1015-C1815?
Very good move changing to the TIP35/TIP36. The TIP41/TIP42 are good transistors- I have used them often- but they are only really suitable for around 20W. The TIP35/TIP36 will not only be more reliable, but have a more suitable hFE curve for a 40W amp. Later, you would be able to increase the supply line to 60V and get about 90W with the same transistors and a couple of resistor changes. The other advantage is that the TIP35/TIP36 have a larger case which is better for heat sinking. Make sure you get the B, or better still, C versions. How would you feel about using TIP41/TIP42 as drivers in place of the 2SC2383/2SA1013 driver pair. If you are prepared to go that way I will investigate and advise.
R19 and C11 are there to tailor the open-loop frequency response (OLFR). The values will depend on your final layout, final transistors, and the final gain that you want. If needed, the values will be around, R19 = 4K7 and C11 = 1nF. Just allow room for them on your layout. They may not even be necessary. In any event, I will have to do some detailed analysis and refer to a bible on the subject to optimise the amp overall OLFR. Don't worry about frequency response in the audio band (20Hz to 20KHz) that will always be flat. The OLFR is another matter altogether. Many amps simply don't tailor the OLFR and they work fine, so it could be that R19 & C11 will not be necessary; I simply can't tell at the moment.
The voltage gain of the amp, in the audio frequency band, is defined by 1 + R4/R13 only. So at the moment, the gain is set to 1 + 4K7/100R = 48. This is higher than normal which would be around 30, but I have made the gain high because I think you are intending to use the amp without preamp. A lower gain, and thus more negative feedback, means correspondingly lower distortion, although not significantly so. If you did want to lower the gain in line with convention, you would need a pre amp, which is the way that I would go as a matter of course. The gain setting of the amp changes the OLFR requirements, which is in accordance with classic negative feed-back theory, a good subject for a budding engineer to learn about.
Merry Xmas!
