Favourite circuits for CC generator ?

[Winfield Hill]

ChrisGibboGibson wrote...
Sorry, folks, I meant to say the TLV431, which controls its HI pin:

| +V o current sink out
| | |
| 100k ||-' 2N7000
| | ||<- 2N7002 (smt)
| +---||-+
| \__|__ | 1.24
| / \_____| I = ---- = 1.0 mA
| TLV431 /___\ | R R
| | 1.2k
| | |
| GND ---+------'

Yeah I'm still working on that and making no progress.

Easy. :>)

Use the LM385 here (it controls its LO pin), with a p-type mosfet.

| +V ---+------,
| | | R
| \__|__ 1.2k 1.24
| / \_____| I = ---- = 1.0 mA
| LM385-adj /___\ | R
| | |
| +---||-+ VP0106N
| | ||-> bss110
| 100k ||-, bss84 (smt)
| | |
| | o current source out
| ===
| GND

 

[Fred Bartoli]

ChrisGibboGibson wrote...

Sorry, folks, I meant to say the TLV431, which controls its HI pin:

| +V o current sink out
| | |
| 100k ||-' 2N7000
| | ||<- 2N7002 (smt)
| +---||-+
| \__|__ | 1.24
| / \_____| I = ---- = 1.0 mA
| TLV431 /___\ | R R
| | 1.2k
| | |
| GND ---+------'

Easy. :>)

Use the LM385 here (it controls its LO pin), with a p-type mosfet.

| +V ---+------,
| | | R
| \__|__ 1.2k 1.24
| / \_____| I = ---- = 1.0 mA
| LM385-adj /___\ | R
| | |
| +---||-+ VP0106N
| | ||-> bss110
| 100k ||-, bss84 (smt)
| | |
| | o current source out
| ===
| GND

Bummer! Guess what : I've just discovered I've always assumed the 385-adj
controled its top pin like the 431, and never bothered to check the DS, just
working from bad memory.

Still I win on transistor count and yours is vastly over engineered

 

[ChrisGibboGibson]

ChrisGibboGibson wrote...

Sorry, folks, I meant to say the TLV431, which controls its HI pin:

| +V o current sink out
| | |
| 100k ||-' 2N7000
| | ||<- 2N7002 (smt)
| +---||-+
| \__|__ | 1.24
| / \_____| I = ---- = 1.0 mA
| TLV431 /___\ | R R
| | 1.2k
| | |
| GND ---+------'

Easy. :>)

Use the LM385 here (it controls its LO pin), with a p-type mosfet.

| +V ---+------,
| | | R
| \__|__ 1.2k 1.24
| / \_____| I = ---- = 1.0 mA
| LM385-adj /___\ | R
| | |
| +---||-+ VP0106N
| | ||-> bss110
| 100k ||-, bss84 (smt)
| | |
| | o current source out
| ===
| GND

Now that I do like.

Cheers

Gibbo

 

[John Woodgate]

I read in sci.electronics.design that Winfield Hill

Sorry, folks, I meant to say the TLV431, which controls its HI pin:

Do these arrangements produce a predictable source resistance or is it
just 'very, very high'?

 

[Fred Bartoli]

I read in sci.electronics.design that Winfield Hill


Do these arrangements produce a predictable source resistance or is it
just 'very, very high'?

These source resistances are very, very, very, very very, very high.

Even the simple one with a single transistor is over 1G.

You still can render them predictable with and additional resistor

 

[Rich Grise]

Bummer! Guess what : I've just discovered I've always assumed the 385-adj
controled its top pin like the 431, and never bothered to check the DS,
just working from bad memory.

Still I win on transistor count and yours is vastly over engineered

But I thought it was a transient response contest!

Cheers!
Rich