100mA CCS?

Bricolo · 22nd February 2004, 08:12 AM

Hi,

I'm looking for a CCS schematic, that will be used to feed a TL431 regulator (that iteslf, will feed a DAC)

The voltage compliance is not an issue (within some limits...)

What could I use for this? Is a simple BJT+LED+resistor good enough?

And, can this CCS+shunt reg be used directly on a raw supply (after the diode bridge) or do I need a voltage regulator before it?

Thanks
Alex

Bricolo · 22nd February 2004, 03:05 PM

Bernhard · 22nd February 2004, 03:11 PM

Which DAC chip you wanna feed ?

Bricolo · 22nd February 2004, 03:48 PM

a 1541

do you have an ides for the current source? I simulated the basic BJT+LED+resistor, the performance isn't excellent

Bricolo · 22nd February 2004, 06:19 PM

no idea?

millwood · 22nd February 2004, 06:19 PM

the datasheet for lm317 has a CCS (a 317+1 resistor). That might be a good / simple solution to try.

It simulated to generate about 0.1ma peak on a 20v+5vp @ 100hz fed.

Pretty good in my book.

Bricolo · 22nd February 2004, 06:31 PM

I was more thinking about a discrete ccs

millwood · 22nd February 2004, 07:19 PM

Bricolo,

this is what I am working on for a preamp. It was lifted from one of those JLH "enhancements".

for this particular one, when fed with 5vp 1000hz ripples on the supply rail, the current fluctuation on the load, Rl, is about 2ua, vs. a steady state of 6.7ma (<0.03%). slightly better than the 317 solution proposed earlier.

you may select different resistors / transistors to make it work at your desired current.

edit: here is the schematic. operator error,

Bricolo · 22nd February 2004, 07:21 PM

Hi Milwood.

This sound nice, but I can't see the schematic

millwood · 22nd February 2004, 07:44 PM

if you take out C1 and R2 (or R3), the current fluctuation through Rl goes up to 8mv (or 1.2% off the steady state current). Not a good thing in my view.

R4 can also be taken out, with a slight improvement.

22nd February 2004, 08:12 AM	#1
Bricolo diyAudio Member Join Date: Nov 2002 Location: Grenoble, FR	100mA CCS? Hi, I'm looking for a CCS schematic, that will be used to feed a TL431 regulator (that iteslf, will feed a DAC) The voltage compliance is not an issue (within some limits...) What could I use for this? Is a simple BJT+LED+resistor good enough? And, can this CCS+shunt reg be used directly on a raw supply (after the diode bridge) or do I need a voltage regulator before it? Thanks Alex

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22nd February 2004, 03:05 PM	#2
Bricolo diyAudio Member Join Date: Nov 2002 Location: Grenoble, FR

22nd February 2004, 03:11 PM	#3
Bernhard diyAudio Member Join Date: Apr 2002 Location: Munich	Which DAC chip you wanna feed ?

22nd February 2004, 03:48 PM	#4
Bricolo diyAudio Member Join Date: Nov 2002 Location: Grenoble, FR	a 1541 do you have an ides for the current source? I simulated the basic BJT+LED+resistor, the performance isn't excellent

22nd February 2004, 06:19 PM	#5
Bricolo diyAudio Member Join Date: Nov 2002 Location: Grenoble, FR	no idea?

22nd February 2004, 06:19 PM	#6
millwood Account Disabled Join Date: Apr 2003 Location: US	the datasheet for lm317 has a CCS (a 317+1 resistor). That might be a good / simple solution to try. It simulated to generate about 0.1ma peak on a 20v+5vp @ 100hz fed. Pretty good in my book.

22nd February 2004, 06:31 PM	#7
Bricolo diyAudio Member Join Date: Nov 2002 Location: Grenoble, FR	I was more thinking about a discrete ccs

22nd February 2004, 07:21 PM	#9
Bricolo diyAudio Member Join Date: Nov 2002 Location: Grenoble, FR	Hi Milwood. This sound nice, but I can't see the schematic

22nd February 2004, 07:44 PM	#10
millwood Account Disabled Join Date: Apr 2003 Location: US	if you take out C1 and R2 (or R3), the current fluctuation through Rl goes up to 8mv (or 1.2% off the steady state current). Not a good thing in my view. R4 can also be taken out, with a slight improvement.

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