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Ld1014d  question about noise
Ld1014d  question about noise
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Old 8th January 2021, 11:47 AM   #1
woody is offline woody
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Ld1014d  question about noise
Default Ld1014d question about noise

In looking at this high power jfet I wonder if it might be suitable for a small low impedance source follower in the 50 to 100ma range. Does anyone know if it would be very noisy when used like that with a 500 ohm source impedance ?
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Old 8th January 2021, 12:59 PM   #2
BesPav is offline BesPav  Russian Federation
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What signal swing are desired?
In the --someVolt range i suppose noise will not be the problem.
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Old 8th January 2021, 01:36 PM   #3
woody is offline woody
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Ld1014d  question about noise
I was thinking about 5v 50 ma at 15v drain to source with a 500 ohm input source resistance at 1k hrz.
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Old 8th January 2021, 01:49 PM   #4
BesPav is offline BesPav  Russian Federation
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For ~100 Ohm headphones?
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Old 8th January 2021, 01:53 PM   #5
Presidentovich is offline Presidentovich  Russian Federation
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Is this an amplifier for speakers???
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Old 8th January 2021, 03:30 PM   #6
BesPav is offline BesPav  Russian Federation
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Quote:
Originally Posted by Presidentovich View Post
Is this an amplifier for speakers???
No.
50 mA idle current follower can't provide enough current to drive speakers.
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Old 8th January 2021, 03:38 PM   #7
jackinnj is offline jackinnj  United States
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Ld1014d  question about noise
Familiar with the Zen8? PassDiy
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Old 8th January 2021, 04:19 PM   #8
MarcelvdG is offline MarcelvdG  Netherlands
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It has a high transconductance and it must have a large die area, so chances are its equivalent input voltage noise level will be quite low. Current noise will be low(*) as long as you reverse bias the gate, which will happen automatically at 50 mA to 100 mA.

(*): Regarding noise current, a smaller JFET will be even better, but you will only notice that at very high source impedances, like those of condenser microphone capsules without built-in amplifier.

Last edited by MarcelvdG; 8th January 2021 at 04:22 PM.
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Old 13th January 2021, 07:58 PM   #9
jackinnj is offline jackinnj  United States
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Ld1014d  question about noise
Here's the Zen9 "noise" -- to get flat frequency response (into a 6 ohm passive load) I had to increase Vds to 2.12, and lower the current to 1.6A. Gain is 21dB.

I've run the LU1014 on its own, not yet satisfied with the results.
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File Type: png Zen9_Noise.png (24.9 KB, 70 views)
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Old 14th January 2021, 06:28 PM   #10
jackinnj is offline jackinnj  United States
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Ld1014d  question about noise
Here's the LU1014D all by itself, powered by Groner's ultra low noise current source (400pA/RtHz), adjusted to 50mA:
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File Type: png LU1014D 50mA.png (33.1 KB, 47 views)
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