1. Only unity gain operation
2. Not possible to add a bias generator (so it will never be anything other than class-b)
3. Inadequate drive from first stage
4. No feedback from output stage which is horrendously non-linear
5. Upper and lower parts of output stage operate in different modes thus have totally different output impedance for positive and negative swings
There's probably some more if I spend more than a minute.
Sorry but it's pointless trying to do anything with this as a power amp. The best you could do would be stop trying to make the output push-pull and convert one of the output devices to a current source. That would gain you class-a operation, but performance would still be very poor especially if run off anything other than a powerful stable supply.
If you want to use n-channel MOSFETs there are circuits around that do the job much better.
2. Not possible to add a bias generator (so it will never be anything other than class-b)
3. Inadequate drive from first stage
4. No feedback from output stage which is horrendously non-linear
5. Upper and lower parts of output stage operate in different modes thus have totally different output impedance for positive and negative swings
There's probably some more if I spend more than a minute.
Sorry but it's pointless trying to do anything with this as a power amp. The best you could do would be stop trying to make the output push-pull and convert one of the output devices to a current source. That would gain you class-a operation, but performance would still be very poor especially if run off anything other than a powerful stable supply.
If you want to use n-channel MOSFETs there are circuits around that do the job much better.
Change the 1meg to something around 220k or 100k. Add another resistor of equal value from the base of the PNP to the positive supply. And change the collector resistor to a 1k pot (this becomes the bias pot).
It'll work fine. Don't expect spectacular performance, but it'll work much better than richie would have you believe.
I'd reccomend class A if you're going to use it open-loop.
Look up the JLH amplifier for more insight into this topology.
It'll work fine. Don't expect spectacular performance, but it'll work much better than richie would have you believe.
I'd reccomend class A if you're going to use it open-loop.
Look up the JLH amplifier for more insight into this topology.
silverchris said:
Another guy, which I gave some advice in this topic,
My simple class A approach, has made a working amplifier!
Not only working, but GOOD WORKING!
Is also jerluwoo FIRST TRYOUT. And almost the same idea as yours.
Even if you use HEXFET and jerluwoo use 2N3055 ordinary big power transistors.
http://www.diyaudio.com/forums/showthread.php?postid=1017622#post1017622
When I say it is almost same, then I mean the output part.
Because jerluwoo, as you can see from schematic
has some input transistor and another one providing Voltage Gain.
As said, your output stage, will give more current to loudspeaker
but the voltage gain will be less than 1 ( less than Unity Gain )
and a power amplifier is most often needed to give
BOTH current gain AND some voltage gain.
I attach the output stage of jerluwoo simple but good WORKING amplifier.
It is the two 2N3055 (NPN) he uses instead of your both N-Channel HEXFET.
lineup
Attachments
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.