>Didn't TI advertise a three-terminal current mirror line some years ago? �It had
>several ratios available, but all NPN (current-sink) polarity. � I never
>saw one, just literature..
The TL011 series--a fave of mine, now long gone (*sniff*). They had 1:2, 1:1, 2:1, and 4:1 versions.
I used to use them for stuff like 5X current multipliers. I still have some, but there's no point in using them.
Cheers
Phil Hobbs
Reply by whit3rd●April 24, 20162016-04-24
On Sunday, April 24, 2016 at 12:01:43 PM UTC-7, Jim Thompson wrote:
> Someone needs to make current mirrors on a chip ;-)
Well, there's the REF200 if you don't mind 'extras';
<http://www.ti.com/product/REF200>
If you saturate the inputs (only takes a volt) on an OTA, you
get a kind of current mirror. Input is diode-clamped to
negative rail, but you can choose the output to be source or
sink, and compliance is good.
Didn't TI advertise a three-terminal current mirror line some years ago? It had
several ratios available, but all NPN (current-sink) polarity. I never
saw one, just literature...
Reply by Jim Thompson●April 24, 20162016-04-24
On Sun, 24 Apr 2016 16:46:58 +0100, piglet <erichpwagner@hotmail.com>
wrote:
>On 24/04/2016 14:31, Jim Thompson wrote:
>>> Yes, an opamp, a comparator and analog switch is a potent combination,
>>> that is what I used to implement the whole of the OP's challenge ...
>>>
>>> Seriously, an opamp, comparator and set of switches would make a good
>>> analog building block kind of chip, does anyone make one?
>>>
>>> piglet
>>
>> Yes. It's called an F-V converter >:-}
>>
>> ...Jim Thompson
>>
>
>Sure, but aren't off-the-shelf F-V chips all prewired so the switches
>are committed to F-V/V-F ? So cannot be configured to do PWM reciprocal
>(like this thread) or PWM square root taking (as we discussed last year)
>or any of all the other things a building block with uncommitted opamp,
>comparator and switches could.
>
>My dream chip would have these pins:
>opampin-, opampin+, opampout
>cmpin-, cmpin+
>switch1 com, switch1 no, switch1 nc
>switch2 com, switch2 no, switch2 nc
>2.45vref out, vdd, vss
>
>the comparator output commutates both analog switches and need not be
>bonded out to a pin. Say 3-16V operation at a few hundred uA, rail to
>rail or at least cmr includes one of the rails, comparator zippy to a
>few 00s ns delay and slower opamp say GBW 1Mhz with nA Ib and mV or two
>Vos. Basically an updated LM392+4053 combo?
>
>
>piglet
>
I could design that for you... for a nominal NRE >:-}
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
The touchstone of liberalism is intolerance
>Hello,
>
>I'm trying to figure out the best way to go about making a -1/x function in hardware. From googling around I see 2 methods,
>
>1. Inverting log -> Anti-log
>2. OpAmp with multiplier in the feedback loop
>
>I have +/-5V rails available, and my input is from 0.4V to 2V (which should give me an output of (-2.5 to -0.5). All DC values.
>
>Can anyone point me in the right direction here, I'm trying to do this with as few parts (no microcontroller) and as painlessly as possible, it doesn't have to be very accurate (2-5% error it ok).
>
>Much Thanks!
Turns out you can just "smoooosh" the function into a single 555, plus
a quad of OpAmps, plus some current mirrors, see...
"MinusOneOverV_555.pdf"
on the S.E.D/Schematics Page of my website.
Someone needs to make current mirrors on a chip ;-)
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
The touchstone of liberalism is intolerance
Reply by Phil Hobbs●April 24, 20162016-04-24
On Sunday, April 24, 2016 at 3:47:10 PM UTC, piglet wrote:
> On 24/04/2016 14:31, Jim Thompson wrote:
> >> Yes, an opamp, a comparator and analog switch is a potent combination,
> >> that is what I used to implement the whole of the OP's challenge ...
> >>
> >> Seriously, an opamp, comparator and set of switches would make a good
> >> analog building block kind of chip, does anyone make one?
> >>
> >> piglet
> >
> > Yes. It's called an F-V converter >:-}
> >
> > ...Jim Thompson
> >
>
> Sure, but aren't off-the-shelf F-V chips all prewired so the switches
> are committed to F-V/V-F ? So cannot be configured to do PWM reciprocal
> (like this thread) or PWM square root taking (as we discussed last year)
> or any of all the other things a building block with uncommitted opamp,
> comparator and switches could.
>
> My dream chip would have these pins:
> opampin-, opampin+, opampout
> cmpin-, cmpin+
> switch1 com, switch1 no, switch1 nc
> switch2 com, switch2 no, switch2 nc
> 2.45vref out, vdd, vss
>
> the comparator output commutates both analog switches and need not be
> bonded out to a pin. Say 3-16V operation at a few hundred uA, rail to
> rail or at least cmr includes one of the rails, comparator zippy to a
> few 00s ns delay and slower opamp say GBW 1Mhz with nA Ib and mV or two
> Vos. Basically an updated LM392+4053 combo?
>
>
> piglet
The AD630 was the last chip that I can think of that worked like that. Thing is, there are lots of excellent fast MUX chips with really low charge injection available for cheap these days, which is what used to be the parlour trick.
So you might just as well use jellybeans and save a lot of money.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net
Reply by piglet●April 24, 20162016-04-24
On 24/04/2016 14:31, Jim Thompson wrote:
>> Yes, an opamp, a comparator and analog switch is a potent combination,
>> that is what I used to implement the whole of the OP's challenge ...
>>
>> Seriously, an opamp, comparator and set of switches would make a good
>> analog building block kind of chip, does anyone make one?
>>
>> piglet
>
> Yes. It's called an F-V converter >:-}
>
> ...Jim Thompson
>
Sure, but aren't off-the-shelf F-V chips all prewired so the switches
are committed to F-V/V-F ? So cannot be configured to do PWM reciprocal
(like this thread) or PWM square root taking (as we discussed last year)
or any of all the other things a building block with uncommitted opamp,
comparator and switches could.
My dream chip would have these pins:
opampin-, opampin+, opampout
cmpin-, cmpin+
switch1 com, switch1 no, switch1 nc
switch2 com, switch2 no, switch2 nc
2.45vref out, vdd, vss
the comparator output commutates both analog switches and need not be
bonded out to a pin. Say 3-16V operation at a few hundred uA, rail to
rail or at least cmr includes one of the rails, comparator zippy to a
few 00s ns delay and slower opamp say GBW 1Mhz with nA Ib and mV or two
Vos. Basically an updated LM392+4053 combo?
piglet
Reply by Jim Thompson●April 24, 20162016-04-24
On Sun, 24 Apr 2016 09:09:10 +0100, piglet <erichpwagner@hotmail.com>
wrote:
>On 23/04/2016 21:56, Jim Thompson wrote:
>> I considered doing it with a 555, but it takes too many parts. The
>> following is the more accurate equivalent of the transistor, diode, 2
>> capacitors, resistor method... using an OpAmp, a comparator, and 2
>> analog switches...
>>
>> <http://www.analog-innovations.com/SED/F-to-V.png>
>>
>> ...Jim Thompson
>>
>
>Yes, an opamp, a comparator and analog switch is a potent combination,
>that is what I used to implement the whole of the OP's challenge ...
>
>Seriously, an opamp, comparator and set of switches would make a good
>analog building block kind of chip, does anyone make one?
>
>piglet
Yes. It's called an F-V converter >:-}
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
The touchstone of liberalism is intolerance
Reply by piglet●April 24, 20162016-04-24
On 23/04/2016 21:56, Jim Thompson wrote:
> I considered doing it with a 555, but it takes too many parts. The
> following is the more accurate equivalent of the transistor, diode, 2
> capacitors, resistor method... using an OpAmp, a comparator, and 2
> analog switches...
>
> <http://www.analog-innovations.com/SED/F-to-V.png>
>
> ...Jim Thompson
>
Yes, an opamp, a comparator and analog switch is a potent combination,
that is what I used to implement the whole of the OP's challenge ...
Seriously, an opamp, comparator and set of switches would make a good
analog building block kind of chip, does anyone make one?
piglet
Reply by Jim Thompson●April 23, 20162016-04-23
On Sat, 23 Apr 2016 16:42:56 +0100, piglet <erichpwagner@hotmail.com>
wrote:
>On 23/04/2016 15:05, Jim Thompson wrote:
>>
>> Did you miss my post that produces V-to-Period...
>>
>> <http://www.analog-innovations.com/SED/OneOverV_Using_555_Better_2016-04-19_09-02-49.png>
>>
>> Then run this output thru an F-to-V to get the 1/V function.
>>
>> LTspice has many issues with initial convergence. Try setting
>> Solver=Alternate and adding "Spice Directive"...
>>
>> .options plotwinsize=0
>>
>> But don't hold your breath, LTspice still chokes.
>>
>> ...Jim Thompson
>>
>
>Thanks Jim, will try spice tricks. Yes I saw your 555 solution and I
>think it is pretty neat. What F to V would you suggest feeding it with -
>just so we offer the OP and end-to-end solution?
>
>piglet
I considered doing it with a 555, but it takes too many parts. The
following is the more accurate equivalent of the transistor, diode, 2
capacitors, resistor method... using an OpAmp, a comparator, and 2
analog switches...
<http://www.analog-innovations.com/SED/F-to-V.png>
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
The touchstone of liberalism is intolerance
Reply by Jim Thompson●April 23, 20162016-04-23
On Sat, 23 Apr 2016 17:04:40 +0100, piglet <erichpwagner@hotmail.com>
wrote:
>On 23/04/2016 16:57, Jim Thompson wrote:
>>> Thanks Jim, will try spice tricks. Yes I saw your 555 solution and I
>>> think it is pretty neat. What F to V would you suggest feeding it with -
>>> just so we offer the OP and end-to-end solution?
>>>
>>> piglet
>>
>> That's a chip function that's available off-the-shelf, but to keep the
>> ignorati braying, I'll try making one from a 555 >:-}
>>
>>
>> ...Jim Thompson
>>
>
>Yes, and I was thinking an LM2907 kind of thing a bit overkill. Can you
>do something minimalist with just a C and Q and arrange the transistor
>temp coeff in the F-V to cancel with Vbe TCs in the current sources
>around the 555 ? :>
>
>piglet
>
There's an ultra-simple "tachometer" F-to-V circuit using one
transistor, one diode, two capacitors and one resistor, but it has a
2-Vbe offset.
I used it a gezillion years ago in a smog control element for
automobiles.
I'll see if I can adapt it.
(The effect of the Vbe TC's in the current mirrors is pretty small...
and it's trivial to add an OpAmp to make it approach zero, so I think
it's better to make the F-to-V TC zero as well.)
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
The touchstone of liberalism is intolerance