Tube DIY Asylum

RE: CASCODE...

76.90.100.230

Tre'

In Reply to: RE: CASCODE... posted by PakProtector on April 18, 2024 at 07:43:59

If I'm doing 10ma through a plate load CCS does the DN3545N3 under a 10M45 need a heat sink?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
https://www.mouser.com/ProductDetail/Microchip-Technology/DN (Open in New Window)

Edits: 04/19/24 04/19/24

Follow Ups:

RE: CASCODE... - PakProtector 17:54:43 04/20/24 (6)
The 'under' element has just the upper element bias voltage across it drain-source. Sooo...with 3V for the DN3545N3 to hide under at 10 mA, dissipation is 30mW. IOW, I really doubt it will need a heatsink.

Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
- Any idea how they bias up? - Tre' 16:38:50 04/22/24 (4)
  The 10m45s have this nice chart on the datasheet but I don't see that with the DN3545N3.
  
  Tre'
  Have Fun and Enjoy the Music
  "Still Working the Problem"
  - sure... :) - PakProtector 01:32:17 04/24/24 (3)
    The datasheet linked through the digikey site has two sets of plate curves. the more detailed set has D-S voltage from 0-10V. It is not the bias R sort, but just as you'd use a set of screen-grid-less pentode curves to determine bias R, you should use those...
    
    These are MOSFET's, not dedicated current regulators, yes?
    
    Douglas
    
    Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
    - RE: sure... :) - Tre' 11:06:36 04/24/24 (2)
      Yes, MosFets
      
      sorry for being dense but how does this help me?
      
      Tre'
      Have Fun and Enjoy the Music
      "Still Working the Problem"
      - RE: sure... :) - PakProtector 01:40:18 04/25/24 (1)
        
        In Reply to: RE: sure... :) posted by Tre' on April 24, 2024 at 11:06:36
        
        We are hunting for a current setting resistor, yes? Whilst the 3545 is running beneath a 10M45, right?
        
        So...draw a vertical line at 3V.
        
        Then join me in the guess that we want about 1.7V for operation at 20-30 mA.
        
        Apply Ohm's Law to determine the resistance required to deliver 1.7V at this idle current. Unless you wish to run 50 mA...in which case, note there is a gate line at that current( the -1.5V lowest one ).
        
        Since the 1.7 is a guess/interpolation be prepared to adjust this value a bit. I suggest some battery bias to bring the effective bias voltage up to ~12 so most of the resistance is dedicated to covering the battery's extra voltage.
        
        Douglas
        Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
        
        RE: sure... :) - Tre' 11:44:12 04/25/24 (0)
        
        In Reply to: RE: sure... :) posted by PakProtector on April 25, 2024 at 01:40:18
        
        Yes and yes.
        
        I get it but I'm doing 11 ma. for my drivers and 10ma for the second stage of my phono preamp and 2.3ma for the first stage of my phono preamp.
        
        I just used trim pots to find what value Rset resistance I needed in each instance. It's all working fine now. Thanks.
        
        Tre'
        Have Fun and Enjoy the Music
        "Still Working the Problem"
- Thank you. nt - Tre' 07:17:09 04/21/24 (0)
  .
  Have Fun and Enjoy the Music
  "Still Working the Problem"

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