Stability of 2SK170 at small currents - diyAudio
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Old 21st November 2009, 09:13 PM   #1
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Default Stability of 2SK170 at small currents

Normally we run the 2SK170 well over 5mA when used as gainstages.

Intend to use a 2SK170 as a simple CCS at 0,1mA and ca 30V over it. Will there be any drawbacks at the low currents I mentioned?
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Old 21st November 2009, 09:20 PM   #2
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Lack of speed + excessive noise i would guess.
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Old 21st November 2009, 09:28 PM   #3
jcx is online now jcx  United States
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large parasitic C with the large die makes for a very poor ccs at higher frequencies
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Old 22nd November 2009, 10:23 AM   #4
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Seems like those drawbacks doesn´t show up in this application, checked with a resistive network instead and no noticeable change.

The third 2SK170 is used as a CCS with 470k to ground. The CCS sets the output voltage through the gyrator whose gate has to be fed high-ohmic to function.

This one will output 30Vrms(B+=75V) into 10kohm with indications of well below 0.1% THD at a Zout of ca 500ohm.
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Old 22nd November 2009, 11:00 AM   #5
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Small error: 30V peak (60V ptp) not 30Vrms. But 25Vrms at below 0,1%.
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