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From: Jim Thompson on 8 Apr 2010 19:48 On Thu, 08 Apr 2010 15:50:27 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1778,C1764,P88400 > >I told these guys to do this, like, two years ago. But they used two >resistors, and I told them to use one. > >John > In the world of discrete's, how much usage would it see? ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: John Larkin on 8 Apr 2010 20:06 On Thu, 08 Apr 2010 19:36:32 -0400, Spehro Pefhany <speffSNIP(a)interlogDOTyou.knowwhat> wrote: >On Thu, 08 Apr 2010 16:21:35 -0700, the renowned John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Thu, 08 Apr 2010 18:12:20 -0500, "krw(a)att.bizzzzzzzzzzzz" >><krw(a)att.bizzzzzzzzzzzz> wrote: >> >>>On Thu, 08 Apr 2010 15:50:27 -0700, John Larkin >>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>> >>>>http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1778,C1764,P88400 >>>> >>>>I told these guys to do this, like, two years ago. But they used two >>>>resistors, and I told them to use one. >>> >>>Neat. Kinda expensive, though (what from LT isn't). A mirror on that would >>>be useful, too. >> >>Yikes, I hadn't noticed the price. That's silly. >> >>John > >Minimum load current of half a mA is a bit high for many >applications.. you'd think they could do better with two resistors. > > Yes, it needs work. But this is the first programmable current source IC that I know of, and it's been an obvious need for a long time. You could cascode this into an RF transistor and make fast ramps without a zillion parts. Now maybe TI and OnSemi will do better ones for 15 cents or something. I sometimes use the small Supertex depletion fets for this. Idss runs around 1.6 mA, and a source resistor will drop that to very low values. But current tolerance is not very good. A multiple-output current source would be cute, too. John
From: Jim Thompson on 8 Apr 2010 20:09 On Thu, 08 Apr 2010 17:06:22 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Thu, 08 Apr 2010 19:36:32 -0400, Spehro Pefhany ><speffSNIP(a)interlogDOTyou.knowwhat> wrote: > [snip] >> >>Minimum load current of half a mA is a bit high for many >>applications.. you'd think they could do better with two resistors. >> >> > >Yes, it needs work. But this is the first programmable current source >IC that I know of, and it's been an obvious need for a long time. You >could cascode this into an RF transistor and make fast ramps without a >zillion parts. > >Now maybe TI and OnSemi will do better ones for 15 cents or something. > >I sometimes use the small Supertex depletion fets for this. Idss runs >around 1.6 mA, and a source resistor will drop that to very low >values. But current tolerance is not very good. > >A multiple-output current source would be cute, too. > > >John Once upon a time TI had a whole set of current mirrors. AFAIK, no more :-( ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: Phil Hobbs on 8 Apr 2010 20:19 On 4/8/2010 8:06 PM, John Larkin wrote: > On Thu, 08 Apr 2010 19:36:32 -0400, Spehro Pefhany > <speffSNIP(a)interlogDOTyou.knowwhat> wrote: > >> On Thu, 08 Apr 2010 16:21:35 -0700, the renowned John Larkin >> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >> >>> On Thu, 08 Apr 2010 18:12:20 -0500, "krw(a)att.bizzzzzzzzzzzz" >>> <krw(a)att.bizzzzzzzzzzzz> wrote: >>> >>>> On Thu, 08 Apr 2010 15:50:27 -0700, John Larkin >>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>> >>>>> http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1778,C1764,P88400 >>>>> >>>>> I told these guys to do this, like, two years ago. But they used two >>>>> resistors, and I told them to use one. >>>> >>>> Neat. Kinda expensive, though (what from LT isn't). A mirror on that would >>>> be useful, too. >>> >>> Yikes, I hadn't noticed the price. That's silly. >>> >>> John >> >> Minimum load current of half a mA is a bit high for many >> applications.. you'd think they could do better with two resistors. >> >> > > Yes, it needs work. But this is the first programmable current source > IC that I know of, and it's been an obvious need for a long time. You > could cascode this into an RF transistor and make fast ramps without a > zillion parts. > > Now maybe TI and OnSemi will do better ones for 15 cents or something. > > I sometimes use the small Supertex depletion fets for this. Idss runs > around 1.6 mA, and a source resistor will drop that to very low > values. But current tolerance is not very good. > > A multiple-output current source would be cute, too. > > > John > How about an LM13700 and a resistor? You can have whichever polarity output you like. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: krw on 8 Apr 2010 20:44
On Thu, 08 Apr 2010 16:48:26 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: >On Thu, 08 Apr 2010 15:50:27 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >>http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1778,C1764,P88400 >> >>I told these guys to do this, like, two years ago. But they used two >>resistors, and I told them to use one. >> >>John >> > >In the world of discrete's, how much usage would it see? I can use this sort of thing, but evidently I'm in the minority since monolithic arrays are going away and Darlingtons are dead. I got away with the MMBT3904 adjacent die parts last time around but my requirements aren't stringent for that circuit. We have another product that we had to do a one-time buy on a Zetex part because the product is dead without it and I'm not sure we *can* design around it (we certainly can't afford a chip). Maybe no one in the discrete world knows how to use current mirrors anymore. |