need really bad diode...

[John Larkin]

On Tue, 20 Sep 2022 19:13:19 -0400, Carl <carl.ijamesxx@yyverizon.net>
wrote:

On 9/20/22 17:20, John Larkin wrote:
On Tue, 20 Sep 2022 13:46:39 -0700 (PDT), Fred Bloggs
bloggs.fredbloggs.fred@gmail.com> wrote:

On Tuesday, September 20, 2022 at 2:04:11 PM UTC-4, John Larkin wrote:
I want lots of voltage drop at 100 mA or so.

A high voltage fast-recovery diode, like ES1G, might work.

I suppose I could just put two ES1Gs in series, but that\'s not
sporting.

MMBD5004S is two wimpy diodes in series, in SOT-23. That would drop
about 2 volts at 100 mA!

This is a supply sequencing dilemma with the LT6803. A long story.

Think of some other way. Diode solutions aren\'t all they\'re cracked up to be.

I just need to drop about a volt. A diode would do that just fine.
Better yet 2 diodes in series so I can tune the drop.

https://www.dropbox.com/s/j72tytvzae0ubf2/T660_Regs_Sep_20.jpg?raw=1

Reg3 has an abs max input of 6 volts. I want at least 6.5 for my
linear regs. I can\'t use 3.3 as the input to reg3 because +1 FPGA core
has to come up before 3.3.


resistor and 5ish volt zener to ground?

Zener regs are very inefficient. The resistor has to be sized for the
max load current, and any less is burned up all the time.

A zener and emitter follower would work. Or a chunky emitter follower
off my +5 supply.

 

[whit3rd]

On Tuesday, September 20, 2022 at 6:35:12 PM UTC-7, John Larkin wrote:

On Tue, 20 Sep 2022 18:23:56 -0700 (PDT), whit3rd <whi...@gmail.com
wrote:
On Tuesday, September 20, 2022 at 11:04:11 AM UTC-7, John Larkin wrote:
I want lots of voltage drop at 100 mA or so.

A high voltage fast-recovery diode, like ES1G, might work.

Or, a diode and 10 ohm resistor in series.

The structure of a PIN diode should give fairly high forward resistivity,
though I\'m not sure where that\'d be found in a datasheet.
HV diodes are usually PINs. That shows up in the I:V curve.

For example, BYT62, from Vishay? It does seem to have the
high forward voltage, and 2.4 kV breakdown...

 

[John Larkin]

On Thu, 22 Sep 2022 01:59:28 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

On Tuesday, September 20, 2022 at 6:35:12 PM UTC-7, John Larkin wrote:
On Tue, 20 Sep 2022 18:23:56 -0700 (PDT), whit3rd <whi...@gmail.com
wrote:
On Tuesday, September 20, 2022 at 11:04:11 AM UTC-7, John Larkin wrote:
I want lots of voltage drop at 100 mA or so.

A high voltage fast-recovery diode, like ES1G, might work.

Or, a diode and 10 ohm resistor in series.

The structure of a PIN diode should give fairly high forward resistivity,
though I\'m not sure where that\'d be found in a datasheet.
HV diodes are usually PINs. That shows up in the I:V curve.

For example, BYT62, from Vishay? It does seem to have the
high forward voltage, and 2.4 kV breakdown...

That looks like a stack, probably three junctions.