Design with Eagle: quad-Op-AMp

[worldcup34]

Hi people ! I'am new to the world of electronic but i have a work for the university to do : design for 60 channels the following circuit with EAGLE (see image 1)

I want to realize a little board (max 4x3,15 inch) so i was thinking to use a quad-opamp (so : 2 opamp for every channel (as you see from the image) = 30 quad-opamp)

Now the problem is the space : someone can help designing just one of these quad-opamp with his relative capacitors/resistors ??

This is what I made (value of resistors/capacitors is not important) (see image 2)

Thank you all , people !!!!!!!!!!!

 

[alec_t]

You won't get 60 channels to fit on one board that size. Perhaps 4 per board?
Draw out the schematic for one channel, using Eagle. Then switch to Board view and arrange the components compactly. Use Auto-route to generate the layout traces. If that's successful you can judge how many channels will fit on a board.

 

[worldcup34]

ok. thank you for the help ! However, how can I dispose component in a way that wires don't cross ?? In fact, uscing the quad-opamp the wire that link with R7 should make junction with pin + of port C. Do you have any idea ??

 

[kubeek]

It might be doable in this size on a double sided plated-through board with small smd packages, but I sure wouldn't want to be the one who has to solder it.

side note: if you can't take the time to prepare this base circuit with just 14 components, how do you plan to place all 30 of those circuits on a single board, with all the connectors, power rails, decoupling etc.?

 

[alec_t]

However, how can I dispose component in a way that wires don't cross ?

Let Eagle's auto-route do it for you. It will create vias (google for that if you don't understand) to avoid cross-overs. You can try different positions of components and compare Eagle's routing efforts.

 

[Boncuk]

Hi,

even with the resistors mounted vertically (pin pitch 0.1") the max number of identical ciruits will be 3X2 OpAmp ICs with their peripheral circuitry.

This number results in a max of 24 fully working OpAmps.

The suggested PCB layout is purely single sided and even using double sided boards that change won't result in 30 circuits.

Chances are good to get all 30 OpAmps on the desired board size (SMD parts) or use my professional Eagle 3.55 version for a through hole PCB design with all components planned.

If you decide using a PCB layout created with my Eagle version you have all possibilities to work with the design - except for one, which is moving parts beyond the border line of 100 and 80mm.

Boncuk

 

[worldcup34]

what do you think about these schematic /board that I made ? Why autorouting command don't create vias for the opamp?? MAny thanks !View attachment 62584View attachment 62585

 

[kubeek]

Because your routing grid setting is too large, so it has no way to connect wires to those tiny pins of the SMD.
Since you are using smd chip, why not use smd resistors as well? I think that you will get much better results if you take more time to properly place the components and route it manually. I use autorouter only in the beginnig of board design to test if the component placement is actually routable, so if the autorouter gets it done to at least 85-90% I know that most likely it is doable manually without using wire jumpers. If the autoruter has serious problems doing it, I know I need to fiddle with the placement some more.

 

[worldcup34]

ok people. That's a sample of my pcb. What do you think about it ? More in detail, what do you think about decoupling capacitor (C29 for V+ and C30 for V-)? Should they be more close to their respective pin or is it ok? View attachment 65747

 

[Boncuk]

How can someone possibly give advise for a board design to finish if there are still tons of unrouted traces (air wires)?

You might be able to to get all your 60 channels routed purchasing the non-profit version of Eagle.

The board size limitation increases from 100X80mm to 160X100mm.

That version will cost you about US$140 to US$160.

Use via dimensions of .9mm dia with a drill size of 0.5mm resulting in a restring of 0.2mm to save routing space.

Don't forget to use decoupling caps at least every 60mm of board space!

Boncuk

 

[worldcup34]

I am currently using EAGLE professional version : this dimension is a choice due to a chamber were will be inserted this PCB. Here a screen of the superior half of the PCB. What do you think about distance components, tracks width ecc ecc ??
Why I can't use 0,25 mm width for signals and 0,4/0,8 mm for supply? Isn'it enough ? Consider that the supply will be around 6 V.
THX!!

 

[Boncuk]

The supply voltage is not critical for a PCB design unless the voltage is mains voltage.

What is the total board current you calculated for 6V supply voltage?

The current decides about the trace width!

Signal traces of 0.25mm are OK to route if the PCB is manufactured professionally.

Check with your board house what they require for minimum trace width and distances!

You could shrink the board length by getting stages closer together.

Your screenshot shows three ICs with four Op-Amps each. There are contained 12 Op-Amps on the "superior half". You planned for 30 Op-Amps total. I'm still missing six Op-Amps in your design.

Boncuk

 

[RichTheDude]

Wider power tracks is always a good thing. If you have the space, go for it!

Try to make ground planes as continuous as possible, Less interruptions = shorter return paths, lower Z, and better performance.

Sure Electronics maybe a good option if you are making the boards daisy chained (i.e. all boards the same).

 

[alisadu]

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