Daqarta and Function generator

What you want is something with high input impedance to buffer your sound card this could be an emitter follower. Then you feed the output of this to a gain stage like say a Common Emitter how many stages depends on the amount of gain, you could then buffer this with a diode compensated push pull stage.

Heres a pic of what I said. Output stage of a DDS based signal generator.

You will need a separate power supply for the amplifier! Be careful you don't fry your soundcard!

Keywords to use for your power supply are "current limiting" and "foldback current limiting"

Some bjt tutorials.

I strongly suggest you read and understand the tutorials and understand your soundcard before arbitraly hooking components to it. This could get expensive.

There is enough information to get you started.

Good luck

That is an example only!!

Kari:

You don't mention what you intend to use the amplified function generator outputs for... that might make a big difference in recommendations.

The best and cheapest amplifier will probably be a home-stereo amp (or the amp part of a receiver). You may already have one on hand, or pick up an older model (cheap or free) from someone who is upgrading. The Velleman kit is 50 watts/channel into 4 ohms or 40 into 8 ohms (real watts, not "music power") which are fairly common home stereo specs.

Note that sound card outputs are AC-coupled, just like stereo amps (including the Velleman, I suspect, since they don't claim otherwise), so you will not be driving any DC loads.

It's possible to modify a cheap sound card to have DC outputs, and it's fairly easy to modify most stereo amps to have DC outputs, but these are not good projects for beginners since it is too easy to "let the magic smoke out."

If you are just in the process of setting up a general purpose home lab, I'd advise against any external amplifier for the function generator until you have a specific need. You may discover you don't need anything more than the sound card puts out already.

Sound cards are usually well protected against output load problems, and in fact handle (or at least tolerate) low-impedance headphones. The raw output is likely all you need to drive most test situations, like frequency response and distortion measurements.

Best regards,

Bob Masta DAQARTA v5.10 Data AcQuisition And Real-Time Analysis

THANKS ! indeed ....

Kari

What you mean with this...Do you mean I should buy some books or something? If so ISBN is? My attention span is very bad indeed, it has always been. Nowadays they even have a diagnosis for it...

Thanks did not notice it.

Best Regards Kari

I had an analog meter when I was 12, and soon it no longer worked, the needle having wrapped around the stop too hard. I was careful of any later meters, having learned the lesson.

Or, that time when I touched high voltage and when I pulled away my elbow slammed into a hard surface enough to hurt, I was careful of high voltage after that.

In other words, actually doing mild damage may be a better way of preventing accidents than merely warning someone to not do something because it might cause an accident. Michael

Well...main reasons - it would be "cool". I though that it would open possibilities to test different things.

- solenoids

- transformers

- inductors

- PWM

and so ... mainly I am just curious. But like you say I might not even need it.

This is a good idea - I try to find used amplifier which I don't mind destroying.

Ok

Ok - I won't try it yet.

I put it in the back burner - the Velleman that is. One other helpful person gave two links and I am going to spend some days reading those - very good sites!

OK

Now when I have you attention you hopefully don't mind a question.

How to find out capacitance and inductance with using function generator and scope? Is it easy,not so easy, hard, very hard or impossible? I remember seeing this somewhere in the net, but don't find it now.

Best Regards Kari

Johns giveing you a nice detailed instruction but I see from your sig that you are at least familiar with PIC's so you could build your own.

Here is a pretty good one.

I should have mentioned that I am not totally ignorant about electricity and electronics. I know the passive components quite well but transistor has always been difficult to me. I had electronics as hobby when I was a kid up to something round 16 years old. Then I was in the UNI and learned something(I am a dropout). Then worked in computer business. Now I am retired and though that why not...

I have had 220V chocks something round 5 times totally in my lifetime and they really hurt. Luckily the hart was not stopped. Nowadays I triple check before touching anything. But naturally accidents could happen. I am mainly interested the low-voltage electronics (at least now).

The amplifier thing I mentioned turned up nicely. I got used car audio amplifier for about $90 from auction site in Finland.

Specs:

APA4400G

So is this good one or bad?

I have never worked with car amplifiers. But I think it must be single supply 12V with lot of amperes (I have a lab power supply which probably can cope). And what is good that according the manual there seems to be all possible protections for misuse. I only hope the seller is honest...

Well another new tool to play...:-)

By the way these newsgroups are great. I have learned a lot when reading these groups. I use GigaNews which has retention to year 2003. Groups about electronics, interesting me contains about

Best Regards Kari

How about 15 watts VHF right into the palm of your hand. That is an attention getter. Won't touch that again.

Thank you! Even I understood. If you have time the second method would be interesting.

Best Regards Kari

Ok thanks. That should be interesting project to make. And also easier to use. Will save the link and do it later.

Best Regards Kari

You hit the nail on the head with your observation about the 12V power supply. My personal feeling is that even if this amp is free it will not be worth the effort and expense of getting it working on your bench. I'd vote to hold out for a cheap home stereo amp. Even units from 40 years ago should be fine for this. I imagine that as people buy 5- and 7-channel "home theater" systems, their old 2-channel units will be cheap or free.

Best regards,

Bob Masta DAQARTA v5.10 Data AcQuisition And Real-Time Analysis

Ok Bob, Thanks! Will keep eyes open.

Best Regards Kari

OK.

For the cap, set up your equipment like this: E1 +-------+ |