Dual discrete opamp PCB in DIP8

[tiroth]

Here is a potential layout for moamp's discrete opamp, designed to simulate a standard dual opamp. The idea is to use it with Jen's Active Filter 2 board. Of course, it could also be used in any other circuit as an opamp replacement.

There will likely be a group buy of these boards

You can see that the design will plug in Jen's board in DIP8, plus the two grounds into the bypass capactor pads. I have also laid it out to be used in a DIP12 pad for use in other designs. I'm not sure how critical the ground connections are as long as the host circuit has the appropriate components...

Please let me know any comments on the layout so that it can be improved. Thanks!

[tiroth]

Here is the corresponding schematic. It should match moamp's schematic . I included R10.

The other half merely has the resistor numbers + 10.

Warning! All of the 3-pin transistors are backwards in the schematic. This is because my schematic library had the pinouts backwards and I was too lazy to create new models. They should be correct on the PCB.

[tiroth]

Since the board is so compact, this is a better visualization:

[moamps]

Originally posted by tiroth
[B]Here is a potential layout for moamp's discrete opamp, designed to simulate a standard dual opamp. The idea is to use it with Jen's Active Filter 2 board.

Hi,

If the discrete opamp is going to be used in Jens's board, some parts can be left out. R10 is necessary for DC stability and can be soldered directly onto the bottom side of the motherboard (from pins 1 and 7 to the ground), and an additional ground wire isn't necessary.

Regards

[BDP]

Tiroth,

Would it be a good idea to be able to adjust the output offset to zero volts? One of the drain resistors could have a footprint to accomodate an adjustable pot.

Moamps,

You obviously have board files for MOX and I dont remember anyone just asking if you would be willing to supply the files to someone so they could do a group run of your layout. I know we could make are own or do a perf. board, but a finished PCB is so neat and clean. PCB's give it that professional look!! Well, enough begging for now. I do thank you for all that you have contributed on this X-over.

BDP

[millwood]

has anyone thought about making this thing pin-compatible with the standard dip8 dual opamps?

For example, you can break up the board into two pieces, each containing one opamps. On one side of the boards, you will have your input pins and output pin, and insirt each board into one bank of a dip8 socket so that they will be drop in replacement of typical dip8 opamps.

Wouldn't that make this thing more marketable?

and if you used smd parts,

[lumanauw]

In Mr. Borbely's paper about Jfet, they are divided to 3 classes, based on current. The GR BL V.
Building this discrete opamp doesnt have to know that data? Any K389 in the market will work?

[MBK]

Now we're talking

I suppose there will be a wiki / a prospective buyer list?

And, yes, it would be most useful as a pin compatible dual op amp replacement - I was thinking of building those with point to point wiring (would be a ball of components I guess) for easy drop in into legacy projects, or simply to compare with standard op amps. Also, it would fit any other PCB designed for dual op amps etc etc etc. That would definitely tickle many a fancy.

MBK

[tiroth]

Originally posted by millwood
has anyone thought about making this thing pin-compatible with the standard dip8 dual opamps?

That's rather the point.

For example, you can break up the board into two pieces, each containing one opamps.

That's an interesting idea. You'd have to link the two halves though via wires in order to tap the bipolar supplies out of the opamps. It would probably make it compatible with more uses.

Thanks for the insight moamps. I will take it into consideration and simplify the layout further.

I'll also set up a wiki tomorrow and provide more details on a group order.

[tiroth]

The thread for this group buy is here:
MOX-like crossover and discrete opamp group buy

The group buy wiki is here:
http://www.diyaudio.com/wiki/index.php?page=Moxbuy

I will have the opamp PCBs redone tonight incorporating millwood's design suggestion. Stay tuned.