bocka said:
OH! That was just me sticking a bunch of diodes into a schematic that Frank had posted previously here.
Yes, you're right, the ZEN V5 is a push pull amp. But with one additional cap to the gate of the BUZ905...
se
I have tried a number of one-transistor amplifying circuits with BJT's and power MOSFET's. The only amp that could be considered as a very good sounding (in terms of high-end) is the one that I am attaching. The current source in Source branch is a must to obtain low distortion. Inductance or resistors or bulbs used instead of the current source are interesting challenge but do not lead to good sounding circuit.
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so whats better?
In a source follower:
A) Use a choke load and a 4700-10,000uf coupling cap?
B) Use a 1:1 OPT load with no coupling cap?
This is with a circuit that is 24vdc supply and 4A bias on a MOSFET.
Just wondering if I should try the OPT or just choke load it with a coupling cap....?
Thanks!
so whats better?
In a source follower:
A) Use a choke load and a 4700-10,000uf coupling cap?
B) Use a 1:1 OPT load with no coupling cap?
This is with a circuit that is 24vdc supply and 4A bias on a MOSFET.
Just wondering if I should try the OPT or just choke load it with a coupling cap....?
Thanks!
I think a choke and a good quality coupling cap might be the easiest way to get a good sounding amp. Transformers are tricky to get right I think. OTOH a 1:1 transformer operating at low voltages can be bifilar wound, which should be an advantage.
If you´re giong to wind your own stuff a choke will definitely be easier.
If you´re giong to wind your own stuff a choke will definitely be easier.
25Vdc x 4A = 100W, you´ll need a big one! I´d suggest you use two or three mosfets in // with adequate source resistors for current sharing. There are plenty of Mosfets suitable for this, say IRFP 140, IRFP 150 or something like that. Plenty of Mosfet disussions in the Pass labs forum.
A "flyback" diode from source to drain might be necessary, but those are often integrated in modern mosfets.
BTW it seems that protecting diodes has been up in this thread before...
I´d use 3x 2200uF low ESL/impedance caps. Caps made for switching PSU´s are usually low loss types, look for such.
Remember to bypass with quite a few uF of nice plastic film caps, or even better, paper in oil caps.
A "flyback" diode from source to drain might be necessary, but those are often integrated in modern mosfets.
BTW it seems that protecting diodes has been up in this thread before...
I´d use 3x 2200uF low ESL/impedance caps. Caps made for switching PSU´s are usually low loss types, look for such.
Remember to bypass with quite a few uF of nice plastic film caps, or even better, paper in oil caps.
You will have to know thermal resistance of the transistor (depends on package and chip), insulating pad and heatsink. Take into account that 1°C/W of the summarized thermal resistance will cause 100°C increase of chip temperature (provided there is a 100W power dissipation).
janneman said:
The 2SK60 and it's complementary device 2SJ18 are both enhancement types which were used by Sony in for instance their TA-N7 in the late 70's.
They were used as cascodes for the output stage, which had low-voltage bipolars driving the load.
Jan Didden
Why not the other way round ? Bipolar as cascode for the V-fet ?
OK,
but wasn't the Vfet originally used (in the earlier amps ) for high speed, good linearity and because it is a voltage controlled device ?
But in the TA-N7 ( which I own ) the gain device is bibolar, is this still a Vfet amp ?
Any sense to built a single ended classA amp with N-Vfet and bipolar or mosfet current source ?
but wasn't the Vfet originally used (in the earlier amps ) for high speed, good linearity and because it is a voltage controlled device ?
But in the TA-N7 ( which I own ) the gain device is bibolar, is this still a Vfet amp ?
Any sense to built a single ended classA amp with N-Vfet and bipolar or mosfet current source ?
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