Hello Aniket,
Great work!
Simulation, design, layout, component procurement, assembly, testing and sharing.
This is much more than just DIY, its NPI + sharing!
Again, good job!!
Class-A has minimal to no crossover distortion. But it has two pain areas: low efficiency and manual setting of quiescent current. The latter is the case with any discreet design, anyway.
Have you looked into Composite Amplifier Design?
It uses a very low distortion op-amp for the input stage and a chip-amp for the output stage.
The composite amplifier then gets all the good parameters of the op-amp, like the vanishingly low distortion and high input impedance for the input side and all the required parameters like current gain and low output impedance of the chip-amp, for the output side.
So effectively you end up with best of both worlds without the two pain areas mentioned above.
If good number of people here show interest, we can put together something to begin with.
Again, good job with your Class-A build.
Your figures bring back one question I had about Class A.
In typical Class B amps, the GNFB helps to cut distortion. And since the effectiveness of GNFB reduces with frequency, plus some other factors also reduce their effectiveness with frequency, there is a rise in distortion with frequency. Correct me if I'm wrong.
But the primary source of distortion is crossover distortion. And Class A does not have any crossover distortion. Therefore, shouldn't a Class A amp have a flat distortion profile with frequency? Your amp seems to show this, at least in simulation, whereas most other Class A amps I've seen seem to have a rising distortion profile like a Class B amp. Why do they have this profile?
BTW, can you share the schematic of your amp? What OPS devices are you using?
Hello tcpip,
Kindly excuse me if this is answered in earlier posts.
For a given amplifier, the parameter gain- bandwidth product (gain x b.w) is a figure of merit. It does not change with biasing (class-AB, class-A).
So for a given gain, there will be a definite bandwidth that the amplifier will support.
In the audio amplifier, we tend to further limit that b.w using compensation techniques, to limit the noise.
As we reach towards that limit, distortion increases.
I hope that this helps.
Regards,
Ravindra.
