Hello All,
This is my first stab at a discrete amp. Please be kind. I have been reading about the advantages of cascoding, and I have been hankering to design my own discerete class A/B amp. So here it is. I don't have a good name for it yet.
I have not chosen all the devices yet, but for the output devices I have my eyes on the Sanken SAP-16 or SAP-15 N and P channel dralingtons. These ICs have built in thermal runaway protection and emitter resistors. This just makes this a bit easier. I may also design another output PCB for single transistors including VBE multipliers.
Anyhow, I would very much appreciate if those of you who have designed more than one of these things would take a look at what I have so far.
I have done a lot of homework already, but I would love to do more.
Some notes:
R9 is a timmer to adjust offset.
R11 is a trimmer to adjust bias.
I am hoping to use series CLDs for current sources, but I am not sure if I would run into power dissipation issues... Should I just use a standard NPN bipolar current source?
Thanks for looking!
Cheers!
Russ
This is my first stab at a discrete amp. Please be kind. I have been reading about the advantages of cascoding, and I have been hankering to design my own discerete class A/B amp. So here it is. I don't have a good name for it yet.
I have not chosen all the devices yet, but for the output devices I have my eyes on the Sanken SAP-16 or SAP-15 N and P channel dralingtons. These ICs have built in thermal runaway protection and emitter resistors. This just makes this a bit easier. I may also design another output PCB for single transistors including VBE multipliers.
Anyhow, I would very much appreciate if those of you who have designed more than one of these things would take a look at what I have so far.
I have done a lot of homework already, but I would love to do more.
Some notes:
R9 is a timmer to adjust offset.
R11 is a trimmer to adjust bias.
I am hoping to use series CLDs for current sources, but I am not sure if I would run into power dissipation issues... Should I just use a standard NPN bipolar current source?
Thanks for looking!
Cheers!
Russ
ACD said:Use the diodes in the bias circuit like the seperate diodes used in the Leach amp
Ah yes, I understand you now. When I drew the schematic I did not assume SAP output devices, but yes, if indeed I do use them I will do exactly as you say.
In that case I would omit Q12 and simply add a trimmer I suppose.
Thanks!
Russ
ACD said:Both should work, and gives you much more quick bias setling and temperature compensations
I once made an simple amp using these, and the offsett after 30 min warm up never drifted more than 1 mV
So with Q12 there and mounted on the heatsink, should I safely be able to use other darlingtons? or would I need more than the one VBE multiplier?
You can cascode the inputs regardless of what loads it (and
obviously you know how to do it). It is not essential that you
cascode the inputs, but you might as well make a "theme"
amp out of it, as I did in the 70's with the CAS-1, in which all
the stages were cascoded. AFAIK, it was the first such example.
obviously you know how to do it). It is not essential that you
cascode the inputs, but you might as well make a "theme"
amp out of it, as I did in the 70's with the CAS-1, in which all
the stages were cascoded. AFAIK, it was the first such example.
Nelson Pass said:You can cascode the inputs regardless of what loads it (and
obviously you know how to do it). It is not essential that you
cascode the inputs, but you might as well make a "theme"
amp out of it, as I did in the 70's with the CAS-1, in which all
the stages were cascoded. AFAIK, it was the first such example.
Excellent guidance, Thanks! It is good to know I am not the first!
I had not seen any such amp yet, but then I have not looked all that hard yet.
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