Microscopic Buffer

[waltk]

Just for fun, I thought I would try to make a working circuit, dead-bug style, with SMD parts.  I don't have any experience with SMD, but you have to start somewhere.  I ordered some TL082 chips in SOIC size a long time ago by mistake.  They look like this under my microscope:



Seems like you ought to be able to make a simple buffer out of the opamp, 2 resistors (for bias), and 2 caps (input and output).  I figured (in my ignorance) that you could just flip the opamp over and start soldering parts to the pins.  Here's my first partially complete attempt (abomination):



So lesson 1 is - you can't just solder SMD parts to each other and wire - at least I couldn't.

I decided to make a tiny PCB with some PCB stock that is only 0.22mm thick.  That turned out pretty good, even though the smallest trace is only .01" wide.  Here's the result (etched with the toner not removed yet):



This material is so thin it's almost clear - and easy to cut with ordinary scissors.  Here's the PCB glued to the bottom of the opamp:



After attaching some small wires, the SMD parts,and crimping the right legs over the edge of the PCB, it's done.  It's just as well that this picture is kind of blurry - 'cause it's not too pretty.



After a few unpowered tests for continuity, etc., it fired right up the first time.  Here's the final product - at least until my patience gets recharged enough to mount it in something.

[Morocotopo]

Hey!

That is...

small... no doubt. How are you gonna use it? Looks ideal to mount inside a guitar. Come to think of it, I have some 072´s in SMD format. Hmm....

[waltk]

How are you gonna use it?

Honestly - it'll probably end up in my giant bin of finished-working-unboxed circuits.  It was really more of a learning exercise than anything else (and I still have a lot to learn about SMD fabrication).  I'm beginning to suspect that it would be easier if I had the right tools.   

-Walt

[earthtonesaudio]

Put it *inside* the guitar's volume knob. 

[deadastronaut]

hi walt..

my eyes are bad enough as it is with through hole gear.....smd would finish them off.

cool stuff though.

[mth5044]

That is awesome! Nice job on getting it to work. I love the second picture 

[Gurner]

I took my iphone apart & honestly, it was just like the second picture above (I always wondered how they made things so small to cram it all in that slim space)

A fun exploratory project though ...thanks for the piccies.

[jk-fm]

Mount it inside a battery snap.

[waltk]

Lesson 2 - using hot air is WAY easier than a soldering iron (IMHO).

Here's the second version - done with my trusty old Sears industrial hot air gun.  The hot air gun has adjustable temp and air flow so it's probably almost as good as a real hot air rework station.



Next step; sneak in a couple more 0603 resistors to make a booster. 

[mth5044]

That's just so cool. Too bad the external hardware doesn't shrink down accordingly 

[amptramp]

You could mount it inside a phono plug and have an amplifying cable if you stuck a small key fob battery in with it.

An industrial 4 - 20 mA current loop circuit in a guitar would permit a standard cable to power an amplifier via a current loop receiver.  The bonus is, current loop technology was explicitly designed for high noise environments.  You could have fun with this stuff.