What stuff to buy from Jameco?

Little mosfets, 2N7000 types, are handy. And led's are fun.

John

If it is not in the above list, some LMC555 (low power CMOS 555) CD4066 (quad bilateral switch), CD4053 triple SPDT bilateral switch.

I find the 74HCT259 demultiplexer/addressable latch good for setups where gizmos are controlled from the PC parallel port and such.

(snip)

How about some voltage regulators? I'd suggest some +5V ones for digital, and either +/-12V or +/-15V for those op amps. AND suitable wall-warts (at least 2 or 3 V above the regulator voltage).

Also, with that assortment of op amps, I'm inclined to ditch the 741's.

Regards,

Mark

Do you have any general purpose transistors?

I suggest 10 each of:

And what about diodes:

Transistorwise, i have:

On order already are some 2n7000 power MOSFETs, 3n3819 Jfets and 2n4403 transistors.

Any reason why unijunction transistors, phototransistors, photodiodes, solar cells, photocells, etc are so expensive?

I have no schottky or zener diodes, but I do have:

(snip)

Unijunction transistors are not made in very large volume (if at all, any more) and photo detectors use larger pieces of silicon. But there are some fairly low cost silicon photo diodes available, but I don't know what Jameco carries.

This is an item that is often discounted from surplus places like Electronic Goldmine. They often don't figure out what they are selling.

Some other CMOS logic chips I have used a lot are CD4013 (dual D flip flop for lots of simple uses, like pulse by pulse current limit latching) and the decoded counters like CD4017 (decade) or CD4022 (octal) (good for all sorts of pulse production and sequencing tasks).

Bye. Jasen

I know this isn't exactly what you asked, but I found that I had a huge breakthrough in productivity after I finally broke down and bought a decent stock of resistors and capacitors. Buy in lots of 100 per value to get a better price, and watch for clearance sales, etc. Buy resistors with 5% tolerance at least, but 1% is often not much more expensive, in quantity. You don't have to get every value in the 1% series... get them spaced at 5% or 10% intervals or whatever you can afford. Buy some plastic drawers and keep all values separate.

It is *SO* nice when you are breadboarding a circuit to just reach for the right value, rather than having to sort through a bin (even a bin of all the same multiplier band).

This costs some bucks up front, and yes, I've ended up with a lot of drawers of values I haven't ended up needing. But you can't tell which ones in advance. At the very least buy all the decade values and fill in the rest as finances allow, and as needs come up.

Note that sometimes it is better to have a lot of the same value than a wide assortment, like if you are building ladder D/A converters, or pull-ups on a lot of open collector pins. But in those cases you can probably use 1K or 10K and just replenish with another bag of 100 as needed.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

A guy could actually use these 2n7000s to drive a 4-ohm to 8-ohm speaker with a 100mv guitar source, couldn't he?

thanks

-phaeton

Sure. The absolute simplest amp would place the speaker directly in series with the drain, ac couple the signal into the gate, and use a pot and a series resistor to set positive gate bias... pure class A. Since Gm is around 0.3, you'd get a low but audible speaker level. An output transformer would help, and a 2-stage version would be positively OK.

John

If i'm understanding correctly what "power dissipation" means on the data sheet, then its 830mW ought to put it around the same neighbourhood as the LM386 amps I've played around with. Depending on revision, 386s are 350mW to 500mW, give or take. (I understand that wattage is exponential, etc, so 830mW probably won't sound any louder than 500mW.)

By 'two stage version' do you mean a 2n7000 driving a 2n7000 driving a speaker?

-phaeton

Yeah, might be educational... something like the attached maybe. This is sort of minimalist, so a few more parts would make it better.

John

oops, can't post a pic here. See a.b.s.e.

Got it. Thanks John. (There are too many Johns in this ng, btw)

The reason I asked about this was IIRC I saw a real simplistic amplifier in a Forrest Mimms book using a single 2n7000 and maybe 3 resistors or so- quite a bit like what you have there. I realize that this circuit is really basic and it's not going to sound 'superb' by any means, but sometimes I like to messing around with cheap, kitschy, mediocre-to-horrible amplifiers. I can't explain my fascination, but there it is. Maybe this is why I have a tray full of LM386 and LM383Ts.

$5 says that this setup will actually distort somewhat when played through, which of course, isn't entirely undesireable in the guitar world. I might even throw a high-gain bipolar transistor or Jfet stage in front if it just for kicks... >:-)

Is that a transformer on the speaker, or is that just a speaker? I've never seen one drawn like that before.

Thanks!

-phaeton

(begrudgingly using OutHouse Express today)

Transformer+speaker, pretty much necessary for a single-ended class A beast like this.

It shouldn't distort much unless overdriven. Two more resistors (nfb divider from Q2 drain to Q1 source, and maybe bypass the Q2 source resistor for good measure) would reduce Zout and also reduce distortion, at which point it almost becomes the classic "GE circuit" tape preamp.

Little circuits are fun.

John

Just a 1:1 transformer?

GE == General Electric?

Absolutely.

-phaeton

.....and wouldn't you know, Jameco's website has been inaccessible all day :-(

-phaeton

I went ahead and put the 7400-series grab bag in the cart.

Unfortunately, I don't seem to see any CD4000-series grab bags or assortments from anyone. Well, except eBay.....

-phaeton