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xrk971 Pocket Class A Headamp GB
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Old 25th April 2019, 04:27 PM   #1891
xrk971 is offline xrk971  United States
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Yes, it could apply to the DCA, I sill need re-run the sim with IRF610 and a higher bias current setpoint on the outputs though to get design sorted out.
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Old 29th April 2019, 06:23 AM   #1892
yourownbuzz is offline yourownbuzz  Australia
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nice! would be waiting for an update to the DCA build too!
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Old 29th April 2019, 02:44 PM   #1893
xrk971 is offline xrk971  United States
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Default Low bias JFET DCA

Here is the schematic for the low bias currrent DCA HPA. 118uA bias current for BF82 and 104mA for IRF610:
xrk971 Pocket Class A Headamp GB-bf862-low-bias-irf610-hpa-v1-schematic-jpg

Predicted FFT for 1.4Vpp into 250ohms (THD is about 0.01%):
xrk971 Pocket Class A Headamp GB-bf862-low-bias-irf610-hpa-v1-fft-1-4vpp-250ohm-jpg

Predicted FFT for 700mVpp into 55ohms (THD is about 0.03%):
xrk971 Pocket Class A Headamp GB-bf862-low-bias-irf610-hpa-v1-fft-700mv-55ohm-jpg
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Last edited by xrk971; 29th April 2019 at 02:47 PM.
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Old 30th April 2019, 03:58 PM   #1894
xrk971 is offline xrk971  United States
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Can anyone think of a device that operates with 100uA bias current and has a native speed of 0.400THz or 400GHz?
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Last edited by xrk971; 30th April 2019 at 04:11 PM.
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Old 7th May 2019, 09:02 AM   #1895
knauf1919 is offline knauf1919  Romania
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Q1 can be replaced with J112?
https://www.tme.eu/Document/2ab8d7a6...63e9f/J111.pdf
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Old 7th May 2019, 11:38 AM   #1896
xrk971 is offline xrk971  United States
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J112 is a much bigger 50mA current switch. Might not be the best use for an audio input. BF862 is still available and are the best for this application.
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Old 7th May 2019, 11:48 AM   #1897
knauf1919 is offline knauf1919  Romania
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Quote:
Originally Posted by xrk971 View Post
BF862 is still available...
Where?
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Old 7th May 2019, 01:06 PM   #1898
xrk971 is offline xrk971  United States
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For example, AliExpress - look for code stamped 2AW. Price should not be too cheap.

Online Shop 10pcs/lot BF862 Stamp 2AW SOT-23 original authentic | Aliexpress Mobile

Online Shop 40pcs/lot BF862 Stamp 2AW SOT-23 new original | Aliexpress Mobile

If they send you one not stamped 2AW, file complaint and get a refund. All of ones I have received lately are genuine (checked with JFET Idss matching rig).
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Old 7th May 2019, 01:30 PM   #1899
knauf1919 is offline knauf1919  Romania
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I never bought electronic components on that site but I'll make a try.
Thank you.
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Old 7th May 2019, 01:51 PM   #1900
twocents is offline twocents  South Africa
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Quote:
Originally Posted by knauf1919 View Post
I never bought electronic components on that site but I'll make a try.
Thank you.
I like Aliexpress, but if you want a supplier closer to home:
bf862 jfet | eBay
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