Mr, Prohodimez, The simulation shows reduction of quiesent current from ~155ma to ~135ma on replacing 2N5401 with MPSA92 at input (0) condition. May be this is due to low Hfe of MPSA92. However this remains almost constant at over wide Rail voltage. I think reduction in quiesent current will change the class of operation of Circlophone.
As a designer final view will come from Mr Elvee only.
As a designer final view will come from Mr Elvee only.
Mr. Katiyar, I would like your board in Lay format from #1988. Can I use a matching IRFP250, replace MBR745 to SFAF504G or MUR405, replace Q1-Q2 to matching KEC KTC3200; 2N5401 to Diotec MMBT5401; Q4, Q6, Q13 to Infineon BC846B, 1N4148 and other components to 1206 SMD. R11, R16, R18 to 3512 SMD? I need a compact board.
Can I need match Q5&Q7.
Can I need match Q5&Q7.
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You may check-out Bangla H's mosfet board at post #1810. I think that you can't get any more compact than that with through-hole components. It is based on one of my early layouts which is on daily run. I had tested IRFP250 too, no problem.
Sorry, I don't have this one. I see it in the library list of software simulation packages like Intusoft or Microcap.
Maybe another member can help?
135mA is still acceptable, but anyway you need to build the real circuit to know what the value is going to be: sims are useful, but they have their limits
Though I have made provision of optional gate resistors in the layout but Mr Elvee suggested me in past not to put any gate resistor in the circuit. You may put a short link. Both Input pair and VAS transistors should be matched as far as possible to get minimum offset.
Is KTA1381 equivalent to KSC1381 transistor in electrical characteristics?. If yes then 4.7PF capacitors be used in CB of these transistors as these are 150MHZ transistors.
Is KTA1381 equivalent to KSC1381 transistor in electrical characteristics?. If yes then 4.7PF capacitors be used in CB of these transistors as these are 150MHZ transistors.
Mr Elvee, My last Hexfet Circlophone stereo setup is performing very well connected to audio out of my PC. It is continuously powered on since 7th. No problem of thermal runaway. Temperature is well maintained. It is maintaining quiesent current as well.
Based on the performance of this build I am inspired to build another Hexfet stereo setup but this time with higher DC rail voltage. I intend to use IRFP240 but I think I will not be in aposition to safely take out 100W RMS at 4ohm load with one pair of MOSFET.
I have not yet ordered Toroidal as yet and I need your expert advice as to what max DC rail voltage can I go with one pair of IRFP240. Thanks
Based on the performance of this build I am inspired to build another Hexfet stereo setup but this time with higher DC rail voltage. I intend to use IRFP240 but I think I will not be in aposition to safely take out 100W RMS at 4ohm load with one pair of MOSFET.
I have not yet ordered Toroidal as yet and I need your expert advice as to what max DC rail voltage can I go with one pair of IRFP240. Thanks
MOS Circlophone seems getting the attention that it deserved much earlier. I also have a plan for giving a last shot for a MOS Circlophone with parallel output devices. I have many quality parts around waiting for a chance for a project, so Power Circlophone is a good fit for them.
I have four matched pairs of IRFP240 but I wanted to try something different. I bought AOT11S60 from Aliexpress for curiosity and they appeared quite well matched.
I got these Vgs measurements by following Nelson Pass mosfet matching setup. I used 18V rather 15V that circuit suggests.
A 3.750
B 3.754
C 3.756
D 3.758
E 3.782
F 3.782
G 3.783
H 3.783
I 3.784
J 3.785
K 3.786
L 3.786
M 3.792
N 3.792
O 3.793
P 3.793
Q 3.793
R 3.795
S 3.795
T 3.801
So Elvee, by evaluating the dispersion, does it make sense for going for 4 pairs per channel? Or, are 3 pairs and 2 pairs options more reasonable for you? I know it depends on transformer voltage and wattage but what if I can afford required power supply requirements?
If you take a look at datasheet link above, these are 178 Watt devices even though they are in TO220 package.
I have four matched pairs of IRFP240 but I wanted to try something different. I bought AOT11S60 from Aliexpress for curiosity and they appeared quite well matched.
I got these Vgs measurements by following Nelson Pass mosfet matching setup. I used 18V rather 15V that circuit suggests.
A 3.750
B 3.754
C 3.756
D 3.758
E 3.782
F 3.782
G 3.783
H 3.783
I 3.784
J 3.785
K 3.786
L 3.786
M 3.792
N 3.792
O 3.793
P 3.793
Q 3.793
R 3.795
S 3.795
T 3.801
So Elvee, by evaluating the dispersion, does it make sense for going for 4 pairs per channel? Or, are 3 pairs and 2 pairs options more reasonable for you? I know it depends on transformer voltage and wattage but what if I can afford required power supply requirements?
If you take a look at datasheet link above, these are 178 Watt devices even though they are in TO220 package.
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100W with a single pair is already somewhat excessive, and the limiting factor won't be the supply voltage.
On 4 ohm, it would approximately translate into +/-33V rails.
If you go higher with 4 ohm/single pair, you risk a meltdown in case of an intensive use or a difficult speaker.
With 8 ohm, +/-60 or 65V would be the maximum.
Note that if you use two pairs for 4ohm, each pair will see a 8 ohm apparent impedance.
You can parallel MOSfets without source resistors, provided they are well matched
On 4 ohm, it would approximately translate into +/-33V rails.
If you go higher with 4 ohm/single pair, you risk a meltdown in case of an intensive use or a difficult speaker.
With 8 ohm, +/-60 or 65V would be the maximum.
Note that if you use two pairs for 4ohm, each pair will see a 8 ohm apparent impedance.
You can parallel MOSfets without source resistors, provided they are well matched
Yes it does: the worst case delta if you picked and mixed them randomly would be 51mV, which is perfectly OK, and will be easily swallowed by the 1/gm and Rdson.
Terranigma, check out this rig for matching I built for the last amp:
Unusual amp from 1987
and post
Unusual amp from 1987
I tried all different methods of matching, at different currents, temperatures, etc... and matching was still not even close to perfect in the actual amp....
Vgs was matched very closely under different conditions, but in real amp, voltage on source resistors varied by 20%.
Unusual amp from 1987
and post
Unusual amp from 1987
I tried all different methods of matching, at different currents, temperatures, etc... and matching was still not even close to perfect in the actual amp....
Vgs was matched very closely under different conditions, but in real amp, voltage on source resistors varied by 20%.
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Interesting real-world feedback: it is generally assumed that MOSfets of the same process can be matched accurately based only on a single pair of parameters.
It would be instructive to see what the dynamic behaviour is (I assume you measured the quiescent current).
Peufeu should have the means to test it in his measurement setup.
When he is finished with his main targets, he could investigate that particular aspect
It would be instructive to see what the dynamic behaviour is (I assume you measured the quiescent current).
Peufeu should have the means to test it in his measurement setup.
When he is finished with his main targets, he could investigate that particular aspect
That would be great. I wasted 2 full days on matching them. Cold, hot, different currents, different methods, GD shorted, on common heatsink, no heatsink, etc....
I would say they were perfectly matched, and in the real amp - 20% variety.
the differences were dynamic - depending on temperature, and idle current.
But more or less it was 20%. Hope this amp will work, and 20% is not too bad...
One more thing - I have a little 'transistor tester' that can measure Vgs.
Of course the number it shows had nothing to do with numbers measured in the test (I'm assuming this tester device measures Vgs at
low current, like 1mA to maybe 10mA)...
Relaying on that device is no better then selecting random transistors.
I would say they were perfectly matched, and in the real amp - 20% variety.
the differences were dynamic - depending on temperature, and idle current.
But more or less it was 20%. Hope this amp will work, and 20% is not too bad...
One more thing - I have a little 'transistor tester' that can measure Vgs.
Of course the number it shows had nothing to do with numbers measured in the test (I'm assuming this tester device measures Vgs at
low current, like 1mA to maybe 10mA)...
Relaying on that device is no better then selecting random transistors.
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The actual rig:
Unusual amp from 1987
Instead of measuring Vgs, I simply wanted to find 3 fets with the same voltage drop on the source emitter resistor,
by trying different combinations of fets, and running at the same rail voltage and idle current as my target amp should be running.
Unusual amp from 1987
Instead of measuring Vgs, I simply wanted to find 3 fets with the same voltage drop on the source emitter resistor,
by trying different combinations of fets, and running at the same rail voltage and idle current as my target amp should be running.
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