I bought more than one quad from him and they match for Idss and Vgs as he states. Recently I have added a gain test to my matching routine and his matches are not matched for gain. I will post results of one of his matched quads.
For what he is charging, it would be nice to have Idss, Vgs and gain matched.
If I had a vast pile to work with, I could perform all three tests in the same time as just idss and Vgs. I use the same kind of gear that is used to test devices on wafers before they are sawed into individual devices.
Here is a Punkydawgs quad that I purchased recently. There are 4 transistors worth of characterizations with the P-channel parts first and the N-channel parts last.
You can see that the P-channel parts have twice the gain of the N-channel parts. This may explain some of the gain assymetry in my F4 Beast build.
You can see that the P-channel parts have twice the gain of the N-channel parts. This may explain some of the gain assymetry in my F4 Beast build.
For the perfectionist, trimming is always a compromise.
Patrick
Patrick I expect nothing less from you and all the respect in the world to you.
I purchased from B+D enterprises a few years ago after availability from them was mentioned at this site. I can't recall who, but someone had purchased from them and found them legit on a curve tracer. I see they continue to sell matched pairs:
2SK170BL+2SJ74BL
Steve
2SK170BL+2SJ74BL
Steve
First positive feedback about new seller of 2SJ74| 2SK170 jfet's are show on line today.
Replacement For Toshiba 2SK170/2SJ74
Replacement For Toshiba 2SK170/2SJ74
Attachments
can low power MOSFETS like zvn3310 - zvp3310 be used at the input stage of preamps/amps in place of low power jFETs 2sk170 - 2sj74, in the complementary input stages like in BA-3 or in LTP input stages as in aleph series, BA-1/BA-2?
(may be cascoded to reduce the input capacitance in either cases)
(may be cascoded to reduce the input capacitance in either cases)
As a concept, yes. However, other characteristics aside, these Jfets are
depletion mode, so they will conveniently bias themselves up without
external circuitry. The ZVN and ZVP have to be given either a bias
voltage at the Gates (relative to their Source pins) or biased by a
current source of some kind. In this sense, it is often simply a matter
of convenience to use the Jfets.
depletion mode, so they will conveniently bias themselves up without
external circuitry. The ZVN and ZVP have to be given either a bias
voltage at the Gates (relative to their Source pins) or biased by a
current source of some kind. In this sense, it is often simply a matter
of convenience to use the Jfets.
Just checking at the option.. as here we have both n and p types of these low power mosfets available easily and at relatively lower cost.
So aside from biasing, how would they be when used in BA-3 (symmetric circuit) or LTPs (input stages) instead of the jFETs.
These MOSFET's input capacitance is higher when compared with jFETs , so do we need to go for adding cascode transistors to them?
Are there any other alternatives for depletion mode devices?
Cascoding is beside the point. Enhancement-mode devices, like virtually
all the Mosfet you might encounter, require some voltage between Gate
and Source pins before they will conduct current.
For an N channel Mosfet, that voltage would be positive relative to the
Source, and for a P channel Mosfet it would be negative relative to the
Source.
Depletion mode devices want to conduct current in the absence of
Gate to Source voltage. Think of a tube. For an N channel depletion
mode device, you have to apply negative voltage between the Gate
and Source to turn the current off, just as you would have to apply
negative voltage between the Grid and Cathode of a tube to shut it
off.
For an LTP, this would not be an issue, as generally they are biased
by a constant current source attached to the two Source pins of the LTP.
For a complementary input or follower circuit, you need to come up
with some DC bias voltage or current source to put the enhancement
mode parts into conduction. Depletion mode parts often don't need this.
all the Mosfet you might encounter, require some voltage between Gate
and Source pins before they will conduct current.
For an N channel Mosfet, that voltage would be positive relative to the
Source, and for a P channel Mosfet it would be negative relative to the
Source.
Depletion mode devices want to conduct current in the absence of
Gate to Source voltage. Think of a tube. For an N channel depletion
mode device, you have to apply negative voltage between the Gate
and Source to turn the current off, just as you would have to apply
negative voltage between the Grid and Cathode of a tube to shut it
off.
For an LTP, this would not be an issue, as generally they are biased
by a constant current source attached to the two Source pins of the LTP.
For a complementary input or follower circuit, you need to come up
with some DC bias voltage or current source to put the enhancement
mode parts into conduction. Depletion mode parts often don't need this.
