simple 150uA constant current supply

"Dave the D*****ad "

One JFET plus one resistor.

D*****ad.

..... Phil

Look up "typical Idss variation for production jfets."

Amateur.

John

"John Larkin" "Phil Allison"

The OP merely needs to chose his FET and resistor ( or trim pot) to get

..... Phil

"Jamie the Lying F****it Asshole "

.... Phil

Phil's been eating too much of the yellow snow. Maybe he'll next lick the frozen flag pole ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

There are microscopic nanopower opamps from Linear and others. Since all you want is nominal +/-20% , and this is the same as Vbatt ranging from

. . . . BATT---+-----------+-----------. . | | | . | | | . [3.9k] | [390] . | | | . | .----|-----------+ . | | | | . | | |\\ | | . | '-|-\\| |< . | | >---------| 2N3904 . +--------|+/| |\\ . | |/ | | . | | | . | | Iout . | | . [166k] | . | | . | | . COM---+-----------+------- . . .

You need to advise someone towards a design that is likely to need a trim pot?

- Don Klipstein ( snipped-for-privacy@misty.com)

Hand selection, trimpots? As I said, amateur.

John

That circuit will usually oscillate, sometimes at two different frequencies simultaneously.

John

Now now children! :)

"Don Klipstein"

The half witted OP is making a one-off - he ain't no designer.

Very wrong of YOU and other "experts " here always * assume * mass production is envisaged.

..... Phil

Phil, please stop licking the bus windows and go play with the barn yarn animals.

Okay, very cool- so he needs to rectify and smooth the output , do you have a problem with that? Seriously, the GBW is like 25KHz...

If the opamp is very slow, as most micropower amps are, the main loop will be stable. But the 3904 may, usually does, oscillate at a couple hundred MHz on its own. A bit of resistance in series with the base,

John

What is it with you people and your oscillating transistors? You do realize the emitter follower load is a 390R resistor? Have it your way: View in a fixed-width font such as Courier.

. . . . BATT---+-----------+-----------. . | | | . | | | . [3.9k] | [390] . | | | . | .----|-----------+ . | | | | . | | |\\ | | . | '-|-\\| |< . | | >---[33]--| 2N3906 . +--------|+/| |\\ . | |/ | | . | | | . | | Iout . | | . [166k] | . | | . | | . COM---+-----------+------- . . .

Yeah, Jamie's getting lonely waiting for you.

-- aioe.org is home to cowards and terrorists

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Here's that same idea using a MOSFET. Don't know how stable with temperature, or how it will vary with production lots.

Paul

==================================================================

Version 4 SHEET 1 1172 680 WIRE 272 80 192 80 WIRE 352 80 272 80 WIRE 480 80 432 80 WIRE 672 80 576 80 WIRE 672 144 672 80 WIRE 192 176 192 80 WIRE 272 192 272 80 WIRE 352 192 272 192 WIRE 496 192 496 128 WIRE 496 192 416 192 WIRE 496 208 496 192 WIRE 192 304 192 256 WIRE 224 304 192 304 WIRE 496 304 496 288 WIRE 496 304 224 304 WIRE 672 304 672 224 WIRE 672 304 496 304 WIRE 224 320 224 304 FLAG 224 320 0 FLAG 192 80 Vin SYMBOL voltage 192 160 R0 WINDOW 0 37 59 Left 0 WINDOW 3 -109 182 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 -109 210 Left 0 SYMATTR InstName V1 SYMATTR Value 3 SYMATTR SpiceLine Rser=20 SYMBOL res 656 128 R0 SYMATTR InstName R3 SYMATTR Value 15k SYMBOL res 448 64 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R1 SYMATTR Value 3.3k SYMBOL res 480 192 R0 SYMATTR InstName R2 SYMATTR Value 220k SYMBOL pmos 576 128 M270 SYMATTR InstName M1 SYMATTR Value FDS6675 SYMBOL LED 352 176 M90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName D1 SYMATTR Value QTLP690C SYMATTR Description Diode SYMATTR Type diode TEXT 320 360 Left 0 !.tran 100m startup

"Fred Bloggs" schreef in bericht news: snipped-for-privacy@nospam.com...

A simple asymmetric current mirror built with a dual PNP transistor - as drawn below - or an NPN part would have much the same accuracy (depending on the Vbe matching between the two transistors in the dual) would probably be cheaper and would use fewer parts, and is unlikely to oscillate.

Farnell stock four NPN and five PNP duals from NXP (was Philips) as well as five current mirrors - three NPN and two PNP three of them from NXP and and two from Infineon (was Siemens). You'd need to look at the data sheets to work out which would suit you best

View in a fixed-width font such as Courier.

BATT---------------+-----------. . | | . | | . [3K9] | . | | . | | . / / . |< |< . | | . +---------+-----------| . | |\\ |\\ . | | | . | | | . | | Iout . | | . [166k] | . | | . | | . COM---+-----------+-------

The 10:1 asymmetry is a bit on the high side - your spare 30uA would accomodate 5:1 - 80k and 1k4

will it work with .8v of supply voltage overhead?

Bob