i was going thru diyopamp by Nelson Pass and got hook on the idea of building a discrete op amp with jfets input(2sk389)
However i have problem sourcing the output stage of the circuit
the circuit calls for a 2vp3310A and 2vn3310A. Can anyone sugest an alternative to this transistors. Also i was wondering about using jfets(sk170) for the ccs. For 4 ma the resistor used is 75 ohm, so for 10 ma i should use 30 ohm resistor rite? Thanks for the help
However i have problem sourcing the output stage of the circuit
the circuit calls for a 2vp3310A and 2vn3310A. Can anyone sugest an alternative to this transistors. Also i was wondering about using jfets(sk170) for the ccs. For 4 ma the resistor used is 75 ohm, so for 10 ma i should use 30 ohm resistor rite? Thanks for the help
Digikey caries both of those MOSFETs just search for VN3310A and VP3310A (it's not listed with the 2 in font). Hope that helps.
Why using fets?
I think you will get yourself a better one with normal transistor,s because off the noise .
GRTZ Don
I think you will get yourself a better one with normal transistor,s because off the noise .
GRTZ Don
the color will be blue so using the 30 ohm sets the current a 10mA rite?
what will be better than fets thaN? bipolar?jfets?
anything other than VN3310A will be better.
what will be better than fets thaN? bipolar?jfets?
anything other than VN3310A will be better.
A normal fast transistor i think will give a better totall result.
The time of the fets which where much faster than bipolair is over.
A freq respons from normal transistor,s will even be higher than the fets and what i mentioned the fet with his input resist is much more sensitive for noise and other hf distortion.
You can see it back in several power output stages .
In the 80,s the power fet was simply better than a bipolair transistor but the time changed with the well known fast transistor,s see the sheets off toschiba nec sanken etc.
Much easier to handle too
The time of the fets which where much faster than bipolair is over.
A freq respons from normal transistor,s will even be higher than the fets and what i mentioned the fet with his input resist is much more sensitive for noise and other hf distortion.
You can see it back in several power output stages .
In the 80,s the power fet was simply better than a bipolair transistor but the time changed with the well known fast transistor,s see the sheets off toschiba nec sanken etc.
Much easier to handle too
NickC said:
Sorry i don,t know this type off operational amp.
The ones you see the most in europe is the ne5532.
A change to an OPA from Burr Brown will give most off the time a more satisfactioner vieuw.
BUT sometimes teh ne5532 will do his work very well and when you used a lott off them parallel with a restistor in the output it will give a much better result than the most expensive op amp for less money
Black with gray legs........why?
How did I know he was going to say that......
Hey Hairy......show us your **TS.
Anyway.....blues......I'll measure a few and let you know.
Ah.......what does speed have to do with constant-current sources anyway? I thought constant current and high impedance where the prime parameters.
Jocko
How did I know he was going to say that......
Hey Hairy......show us your **TS.
Anyway.....blues......I'll measure a few and let you know.
Ah.......what does speed have to do with constant-current sources anyway? I thought constant current and high impedance where the prime parameters.
Jocko
Just as I suspected....
The answer is a resounding NO!
1.) I measured about a dozen at random from my bag o' hundreds, and the Idss is around 7.5 - 8.0 mA (roughly). No way you can get 10 mA from one unless you have violets.
2.) Two in parallel, with a 10 ohm resistor gives a tad less than 10 mA.
I would only use a JFET for a ccs if the current is in the range of a few mA. Go to a bipolar here is my suggestion since you do not wish to use a MOSFET.
Jocko
The answer is a resounding NO!
1.) I measured about a dozen at random from my bag o' hundreds, and the Idss is around 7.5 - 8.0 mA (roughly). No way you can get 10 mA from one unless you have violets.
2.) Two in parallel, with a 10 ohm resistor gives a tad less than 10 mA.
I would only use a JFET for a ccs if the current is in the range of a few mA. Go to a bipolar here is my suggestion since you do not wish to use a MOSFET.
Jocko
jocko
for 4ma ccs, the blue version handles fine rite? should be
Donvandler
the VN3310A is a mosfet, i not familar with it though. More familar with bipolar.
for 4ma ccs, the blue version handles fine rite? should be
Donvandler
the VN3310A is a mosfet, i not familar with it though. More familar with bipolar.
Curent sources using JFET's for above 10 Ma are best handeled by High Idss devices like the 2N4392, PN4392. for N Ch types. and the Classic source to gate resistor will allow you to set the Current to less than the 40 Ma this device can produce with it's gate and source shorted.
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