Very low current CCS?

rdf · 20th June 2008, 12:26 AM

Anyone have experience with <1 ma solid state CCS plate loads? I'm about to grievously abuse an MC240 I've had for 25 years and the front end 12ax7 by my calculation runs at 200 uA Ip on a 100K plate load. It seems the obvious place to start. Thx in advance for any suggestions.

ErikdeBest · 20th June 2008, 11:15 AM

Hi

Morgan Jones (3rd edition) presents a diff pair with an ECC83 with plate loads consisting of MPSA92 transistors set for about 0.4mA (6.2V reference / 16000k), so I assume it could work for loads <1mA...

Erik

Gary P · 20th June 2008, 01:10 PM

Try using cascoded Supertex LND150 MOSFETs. I use them for generating the bias voltage in the self bias CCS (Q2 and Q4) where they run at ~300ua. Very good performing parts. Adjust the value of the 2.2K resistor (R17) up a bit to get 200ua.

Gary P's DIY page

rdf · 21st June 2008, 03:24 AM

Thanks all. The LND150 caught my notice and looks a nice fit for my stock of dsavitsk's PCBs but I couldn't find anyone using them solo as CCSs. Much appreciated!

20th June 2008, 12:26 AM	#1
rdf diyAudio Member Join Date: Jun 2004 Location: big smoke	Very low current CCS? Anyone have experience with <1 ma solid state CCS plate loads? I'm about to grievously abuse an MC240 I've had for 25 years and the front end 12ax7 by my calculation runs at 200 uA Ip on a 100K plate load. It seems the obvious place to start. Thx in advance for any suggestions. __________________ Ears aren't microphones.

20th June 2008, 11:15 AM	#2
ErikdeBest diyAudio Member Join Date: Mar 2003 Location: Itoculo	Hi Morgan Jones (3rd edition) presents a diff pair with an ECC83 with plate loads consisting of MPSA92 transistors set for about 0.4mA (6.2V reference / 16000k), so I assume it could work for loads <1mA... Erik __________________ my surname is indeed 'de Best': neither misspelling nor snobbism! Ask SY!

21st June 2008, 03:24 AM	#4
rdf diyAudio Member Join Date: Jun 2004 Location: big smoke	Thanks all. The LND150 caught my notice and looks a nice fit for my stock of dsavitsk's PCBs but I couldn't find anyone using them solo as CCSs. Much appreciated! __________________ Ears aren't microphones.

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20th June 2008, 01:10 PM	#3
Gary P diyAudio Member Join Date: Apr 2002 Location: Portland OR	Try using cascoded Supertex LND150 MOSFETs. I use them for generating the bias voltage in the self bias CCS (Q2 and Q4) where they run at ~300ua. Very good performing parts. Adjust the value of the 2.2K resistor (R17) up a bit to get 200ua. Gary P's DIY page

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