"Wow! This is going to take ALL DAY to build."
-- attributed to Remus upon seeing the plans for Rome.
-- attributed to Remus upon seeing the plans for Rome.
fet cascoding
Mr. Pass, I found your latest vfet amp in Audio Express interesting. I have some of Sony's older complemetary vfets that I was thinking of cascoding. You used a mosfet to cascode to the vfet. My question is whether a bipolar would work as well as a mosfet for the cascode, especially in not contributing a sonic signature that would mask the vfet. In a complementary pair of outputs, how does the mosfet behave as a cascode in the crossover region where the mosfets are nonlinear but bjts like Toshiba's 1302/3281 are very linear? I'm going to dig out your old Audio Amateur cascode 60W amp to study it's circuit for this project.
Thanks.
Bob
Mr. Pass, I found your latest vfet amp in Audio Express interesting. I have some of Sony's older complemetary vfets that I was thinking of cascoding. You used a mosfet to cascode to the vfet. My question is whether a bipolar would work as well as a mosfet for the cascode, especially in not contributing a sonic signature that would mask the vfet. In a complementary pair of outputs, how does the mosfet behave as a cascode in the crossover region where the mosfets are nonlinear but bjts like Toshiba's 1302/3281 are very linear? I'm going to dig out your old Audio Amateur cascode 60W amp to study it's circuit for this project.
Thanks.
Bob
There's not a lot of difference between using a Mosfet
or a bipolar for the cascode transistor in my book. I
used a Mosfet because I have them laying around like
popcorn.
The cascode transistor imparts very little of its own
character into the signal. With a Mosfet, 100% of the
current through it comes through the cascoded gain
transistor, and the only influence it has is the small
variation in voltage on its Source, which in turn has
a small influence on the the gain transistor, mostly
linear.
With a bipolar, some of the current is sent off through
the Base, so you lose maybe 1% or 2%, but even that
is mostly linear, and doesn't have a lot of effect.
😎
or a bipolar for the cascode transistor in my book. I
used a Mosfet because I have them laying around like
popcorn.
The cascode transistor imparts very little of its own
character into the signal. With a Mosfet, 100% of the
current through it comes through the cascoded gain
transistor, and the only influence it has is the small
variation in voltage on its Source, which in turn has
a small influence on the the gain transistor, mostly
linear.
With a bipolar, some of the current is sent off through
the Base, so you lose maybe 1% or 2%, but even that
is mostly linear, and doesn't have a lot of effect.
😎
Mr. Pass
I thought the idea with using an IGBT operated common base was because signal current does not have to pass through any NPN junctions, but rather a continuous slab of "N" material. Is the capacitance (if any) in a bipolar transistor enough to degrade audio frequencies?
I thought the idea with using an IGBT operated common base was because signal current does not have to pass through any NPN junctions, but rather a continuous slab of "N" material. Is the capacitance (if any) in a bipolar transistor enough to degrade audio frequencies?
All electronic parts have some amount of capacitance. The degree to which it creeps into the audio spectrum depends on the impedance the capacitance sees.
Grey
Grey
No more news?
Hi to all!!!
It would be time for something new, when there'll be a new Zen version?
Hi to all!!!
It would be time for something new, when there'll be a new Zen version?
