silly circuits

I wrote a program that finds resistors in our stock that hit a specified ratio. Because it brackets thevenin impedance, it accidentally also finds parallel resistor combos.

I should fix it to do series too.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

And I can write ECOs to change parts after a board is built.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

The two passive sections have much better ultimate rejection than a second Sallen-Key, which is often a win.

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

{snip]

[snip]

Agreed. ...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

| 1962 | It's what you learn, after you know it all, that counts.

The unity-gain S-K with equal resistor values is pretty good--sensitivity values of about 1, vs. 0.5 for LCs or gyrators. It's the high-gain VCVS ones that have the really horrible sensitivities.

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

But I thought you only had one value of resistor. ;-)

Williams and Taylor lists a bunch of equi-ripple approximations to classic filters, which can be handy.

--
Bill Sloman, Sydney

Using quad r-packs can lock one down. If I suspect that a part might have to change, I use a discrete R or C.

The game is to keep the BOM line count down.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Different worlds. Our job is to keep the cost down. R-packs are expensive but if they can replace four resistors, the placement cost makes up for it. There is no advantage to keep the BOM line count small, though I try to anyway.

We are paying 0.69 cents for a 1K 1% quad resistor pack, about 1206 overall size.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

You can get quad capacitor packs too FYI (don't know if the first circuit has equal values)

--

John Devereux

We are paying less than 1 cent for a resistor pack and with the resistor pack you get very good tracking between the resistors in the package, so some circuits perform a lot better

Cheers

Klaus

We have theorized that the tempcos should match very well inside a pack, but haven't measured it yet.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

I think we pay about 1/4 that for a 0408 4x Rpack and about 1/40th that for an 0402 resistor. It costs something like .25 cents to place either.

That may or may not be true. The Rpacks I've been using don't specify any tracking. If it's not specified, I can't use it.