EDIT:
After getting the bias circuitry working correctly (many thanks to all the members here), this one has evolved to quite an extraordinary little amplifier during the past few years.
So I decided to revisit this thread and post the most recent updates and show how it all looks like today.
Circuit on post #6 updated. Most of the resistors changed and also changes in part labeling, so you can pretty much ignore the later discussion.
For a 100W Class-AB output (8R);
use +/-48V supplies and adjust bias down to 150mA!
THD 1kHz8R is less than 0.001% (with the Toshibas...).
Here is also a "universal" LME49811 PCB which you can use.
There is no reason for not using this one for Darlington output pairs as well. Just replace RB3 with a jumper and adjust Gate (Base) resistors accordingly (start with zero ohms for example).
I actually tested a MJH11021/22 pair with this. I had to change the bias transistor to a darlington type and change Rp to 1kohm and RB1 to 1.2kohm to keep the bias stable and adjustable in a good range.
I used BD681 as Qvbe. But you might want to experiment with that (those)... Anyhow, optimal bias seemed to be around 110mA, at which level the 1MHz 8Vpp signal was clean on the scope.
Some suitable Darlington pairs for the output stage:
BDW63/BDW64
BDW83/BDW84
2SD2083/2SB1383
TIP142/TIP147
MJH11022/MJH11021
...and so on...
If you use the MosFET pair 2SK1530/2SJ201,
change RGN to 365ohm and RGP to 220ohm.
IRFP240/9240 is a no-can-do. LME49811 can barely deliver 5V of bias voltage, which is not enough for the IRFs.
Oh... And the chips GND pin? Yes, its the return for the ShutDown, so all ripple, noise and interference you feed to the SD pin, comes out from the GND. So keep that clean from the audio grounds if you decide to make your own PCB.
Also, if you happen to wonder, how much current does the chip draw during ShutDown? It pretty much shuts down itself also (not only the bias voltage and output signal) and draws therefore MICRO amperes only.
Some high quality gold plated double sided PCBs available for this project. PCB size 61mm x 84mm.
I can sell for 20€ / piece.
PM if interested...
Thanks again, and good luck!
After getting the bias circuitry working correctly (many thanks to all the members here), this one has evolved to quite an extraordinary little amplifier during the past few years.
So I decided to revisit this thread and post the most recent updates and show how it all looks like today.
Circuit on post #6 updated. Most of the resistors changed and also changes in part labeling, so you can pretty much ignore the later discussion.
For a 100W Class-AB output (8R);
use +/-48V supplies and adjust bias down to 150mA!
THD 1kHz8R is less than 0.001% (with the Toshibas...).
Here is also a "universal" LME49811 PCB which you can use.
There is no reason for not using this one for Darlington output pairs as well. Just replace RB3 with a jumper and adjust Gate (Base) resistors accordingly (start with zero ohms for example).
I actually tested a MJH11021/22 pair with this. I had to change the bias transistor to a darlington type and change Rp to 1kohm and RB1 to 1.2kohm to keep the bias stable and adjustable in a good range.
I used BD681 as Qvbe. But you might want to experiment with that (those)... Anyhow, optimal bias seemed to be around 110mA, at which level the 1MHz 8Vpp signal was clean on the scope.
Some suitable Darlington pairs for the output stage:
BDW63/BDW64
BDW83/BDW84
2SD2083/2SB1383
TIP142/TIP147
MJH11022/MJH11021
...and so on...
If you use the MosFET pair 2SK1530/2SJ201,
change RGN to 365ohm and RGP to 220ohm.
IRFP240/9240 is a no-can-do. LME49811 can barely deliver 5V of bias voltage, which is not enough for the IRFs.
Oh... And the chips GND pin? Yes, its the return for the ShutDown, so all ripple, noise and interference you feed to the SD pin, comes out from the GND. So keep that clean from the audio grounds if you decide to make your own PCB.
Also, if you happen to wonder, how much current does the chip draw during ShutDown? It pretty much shuts down itself also (not only the bias voltage and output signal) and draws therefore MICRO amperes only.
Some high quality gold plated double sided PCBs available for this project. PCB size 61mm x 84mm.
I can sell for 20€ / piece.
PM if interested...
Thanks again, and good luck!
Last edited:
I think you can go without the Vbe multiplier circuit in the bias stage with 2SK1529/2SJ200 mosfet.
But you must use large bias current about 300mA.
Also large THD distortion rises because 2SK1529/2SJ200 have large thermal variation.
So distortion level increased.
You can see national semiconductor application note AN-1645 fig. 20.
Where graph with Vbe multiplier shows bias stability , which is not so good.
So you can see itself. 2SK1529/2SJ200 have large thermal variation.
My suggestion is , you must use renesas mosfet 2SK1058/2SJ162 for your application with resistor bias stage.
2SK1529/2SJ200 and 2SK1530/2SJ201 caracterstics are almost same. 2SK1530/2SJ201 have high voltage and currunt rating.
But you must use large bias current about 300mA.
Also large THD distortion rises because 2SK1529/2SJ200 have large thermal variation.
So distortion level increased.
You can see national semiconductor application note AN-1645 fig. 20.
Where graph with Vbe multiplier shows bias stability , which is not so good.
So you can see itself. 2SK1529/2SJ200 have large thermal variation.
My suggestion is , you must use renesas mosfet 2SK1058/2SJ162 for your application with resistor bias stage.
2SK1529/2SJ200 and 2SK1530/2SJ201 caracterstics are almost same. 2SK1530/2SJ201 have high voltage and currunt rating.
bc54xb and thousands of other small signal transistors.
Or use a sot23 NPN glued to the collector leg of one power device where it exits the package. For better tracking of both output devices use an NPN & a PNP glued to both output device collectors. Then use the dual transistor version of the Vbe multiplier.
Or use a sot23 NPN glued to the collector leg of one power device where it exits the package. For better tracking of both output devices use an NPN & a PNP glued to both output device collectors. Then use the dual transistor version of the Vbe multiplier.
Thanks Andrew for your suggestions!
It would probably be better your way, but I was thinking to make this very small and compact.
This is what I have in my mind and actually have all the components for it also.
Will it work?
Questions:
Does the component values seem OK?
Suggestions for CB? Value, type?
I have TIP31 for QVBE, OK?
Will I get a problem, if I used Rs as the volume control at the same time?
Thanks again for all input...
It would probably be better your way, but I was thinking to make this very small and compact.
This is what I have in my mind and actually have all the components for it also.
Will it work?
Questions:
Does the component values seem OK?
Suggestions for CB? Value, type?
I have TIP31 for QVBE, OK?
Will I get a problem, if I used Rs as the volume control at the same time?
Thanks again for all input...
Yes, CB is the Vbe multiplier capacitor.
Cn - noted...
RB3 is needed according to the LM data sheet AN-1645, but I don't know how much I can copy from there directly for this chip???
Gate resistors - noted.
Can I use the values from AN-1645 (500r for P-channel and 175r for N-channel)?
Hello again!
Circuit updated!
NOT WORKING!
I believe it oscillates like crazy, or at least it consumes all power available from the PSU.
No DC voltage at the output.
One channel consumes 95W of power with 10k resistor (RS) at the input. With input short circuited power consumption rises to 110W (55W per rail = PSU max.) - how interesting?
Is my circuit OK? Or do I have a problem with my PCB?
Circuit updated!
NOT WORKING!
I believe it oscillates like crazy, or at least it consumes all power available from the PSU.
No DC voltage at the output.
One channel consumes 95W of power with 10k resistor (RS) at the input. With input short circuited power consumption rises to 110W (55W per rail = PSU max.) - how interesting?
Is my circuit OK? Or do I have a problem with my PCB?
Hello!
I'm using Toshibas 2sk1529 and 2sj200.
If I sorted the source and sink together, I can measure a voltage of -1.12V to gnd.
At the same time the power consumption will drop down to 5W!
This is what I want, don't I?
What is the problem?
Too high resistor values between the source and sink, i.e. way too low bias current???
I'm using Toshibas 2sk1529 and 2sj200.
If I sorted the source and sink together, I can measure a voltage of -1.12V to gnd.
At the same time the power consumption will drop down to 5W!
This is what I want, don't I?
What is the problem?
Too high resistor values between the source and sink, i.e. way too low bias current???
Vgs range seems to be from 0.8V to 2.8V for the Toshibas - am I right?
As my configuration is now, the Fets are running stone cold. It's the PSU which is getting hot as h...
Heatsinks are crazy big compared to the output power i am aiming to (15W/ch) (PSU is +-25V, and limited to 0.5A max to the chip and to 2.5A max for the fets)...
I did not start up the amp with bias down to minimum. But if I do it now (short the sink and source pins?) my major power consumption problem disappears.
Adjusting the bias current to the maximum with the pot, does not solve the problem.
I tried to put a 510R resistor across the sink and source, solves the power consumption problem, but haven't tested anything else yet, like does the amp actually 'amp' that way???
As my configuration is now, the Fets are running stone cold. It's the PSU which is getting hot as h...
Heatsinks are crazy big compared to the output power i am aiming to (15W/ch) (PSU is +-25V, and limited to 0.5A max to the chip and to 2.5A max for the fets)...
I did not start up the amp with bias down to minimum. But if I do it now (short the sink and source pins?) my major power consumption problem disappears.
Adjusting the bias current to the maximum with the pot, does not solve the problem.
I tried to put a 510R resistor across the sink and source, solves the power consumption problem, but haven't tested anything else yet, like does the amp actually 'amp' that way???
Some more tests...
I shorted the 390R resistor - power consumption down to 5W instantly.
N-channel bias +1.03V, P-channel -1.13V...
I also tried a 510R resistor paralleled with the 390R - power consumption 22W. Did not measure the bias voltages.
Am I on the right track here?
Please don't tell me I need to get more voltage out from the PSU to get this working...
PS: Andrew, I would have loved to read your bias explanation... Sorry to hear you had troubles with the forum.
I shorted the 390R resistor - power consumption down to 5W instantly.
N-channel bias +1.03V, P-channel -1.13V...
I also tried a 510R resistor paralleled with the 390R - power consumption 22W. Did not measure the bias voltages.
Am I on the right track here?
Please don't tell me I need to get more voltage out from the PSU to get this working...
PS: Andrew, I would have loved to read your bias explanation... Sorry to hear you had troubles with the forum.
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