Goodmorning everyone ! I have a problem with the aleph scheme! From the original diagrams, it is written that the bias current of the irf9610 mosfets at the input of the input is 20ma! But in making a prototype and inserting an ammeter it measures me 200ma of current! The project still works but I can't understand why I have a higher bias current than the one described by the projects! Do you know anything about it?
Sorry for my English
Sorry for my English
You can select MosFets with a higher or lower gate voltage. I would adjust the bias voltage to compensate.
200mA is too much current!
200mA is too much current!
if that is the case, you have fakes
but, current through input LTP is set with CCS on top, as (Uzener-Ugs)/221R, so (9V1-4V)/220R=5V1/220R=~23mA
if you have higher current through LTP, something is wrong elsewhere, or in CCS itself
but, current through input LTP is set with CCS on top, as (Uzener-Ugs)/221R, so (9V1-4V)/220R=5V1/220R=~23mA
if you have higher current through LTP, something is wrong elsewhere, or in CCS itself
Check if you really have a 221 ohm resistor connecting the positive rail and the upper irf9610. Also check that you
have ~9.1V across the zener near there.
The current is controlled by that resistor and the diff in voltage between the 9.1 zener and the Vgs of that IRF9610.
So with a 221 ohm resistor you shouldn't get anywhere near 200mA no matter your Vgs.
Edit: What ZM wrote.
have ~9.1V across the zener near there.
The current is controlled by that resistor and the diff in voltage between the 9.1 zener and the Vgs of that IRF9610.
So with a 221 ohm resistor you shouldn't get anywhere near 200mA no matter your Vgs.
Edit: What ZM wrote.
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I tried to replace the irf9610 I have with irf9640 and I have 150ma of absorption! I measured the irf610 mosfets and I noticed that the vgs is not 2v but 3.3v! In theory the irf 610 and irf9610 shouldn't have a similar vgs? I measured the voltage you have at the ends of the zener diode and I have 3v and at the ends of the resistor I have a voltage of 40v!
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In this usage, you'll need to have carefully measured and matched your 9610 devices before inserting them into the circuit. It is easy to set up a test jig to match them. This will reveal problems with potential fakes and mismatched devices. Also, be sure to MEASURE every resistor you place in the PCB before soldering it. I've had a number of situations where I ordered 221R and received 220K instead. Wrong values could also account for problems you are experiencing.
See notes on matching these devices in my Aleph-X amplifier page - click the link in my signature and follow it to my Aleph-X page, then scroll down.
See notes on matching these devices in my Aleph-X amplifier page - click the link in my signature and follow it to my Aleph-X page, then scroll down.
Hi everyone ! Finally I discovered the 200ma current problem of the input stage! Unfortunately I made a mistake by connecting the zener diode after the 220ohm resistor! Despite everything I also did another test! I bought some new irf9610 from mouser and checking the vgs I still noticed a big difference compared to the ones I got on aliexpress! The vgs of mosfets taken from mouser is 3.9v while the vgs of mosfets taken from aliexpress is 2 or 1.7v!
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Yep, anywhere near 4v sounds legit. 9610 devices with Vgs of 2v sounds much less legit. Fakes? Static zapped? Who knows? Either way, ditch the ones with 2v or lower measurements.
If you ordered transistors from Mouser in quantities of 25 or larger, you'll likely get a "full tube" straight from the factory. This increases the likelihood that those transistors came from the same silicon wafer during the manufacuturing process. This, in turn, makes it way more likely that you'll find plenty of matched devices when you measure them.
If you ordered transistors from Mouser in quantities of 25 or larger, you'll likely get a "full tube" straight from the factory. This increases the likelihood that those transistors came from the same silicon wafer during the manufacuturing process. This, in turn, makes it way more likely that you'll find plenty of matched devices when you measure them.