Pages: [1]   Go Down
Author Topic: Amplifier  (Read 1428 times)
0 Members and 1 Guest are viewing this topic.
Connecticut
Offline Offline
Edison Member
*
Karma: 17
Posts: 1216
RTFD (Datasheet in our case)
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

So I build this circuit (scroll to bottom of page).

I made the same circuit as shown, but I used an LM358 and 5V arduino supplies. It works (yay!) but there is an annoying overlay of a high-pitched tone. So if I speak into the mic, it is my voice + annoying tone. All my cap + resistor values are correct, I double checked. If it helps:the overlay tone is ~868Hz, according to my tuner.

Is it the op amp that I'm using? The power supply difference?

Thanks for any help!
Logged

0
Offline Offline
Faraday Member
**
Karma: 16
Posts: 2857
ruggedcircuits.com
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Well, you're getting away with a lot of stuff smiley  The circuit is really designed to operate from split power supplies. By connecting the op-amp to +5V and 0V you are going to get a lot of distortion.

Try adding another 100k resistor from the '+' pin of the op-amp to its power supply (5V).

--
The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons
Logged

Connecticut
Offline Offline
Edison Member
*
Karma: 17
Posts: 1216
RTFD (Datasheet in our case)
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Nope. smiley-sad Now there's a softer whine, and no audio from the mic. Guess I'll just stop being lazy and put together a +/-9V supply like I was supposed too. smiley
Logged

Montreal
Offline Offline
Faraday Member
**
Karma: 29
Posts: 2590
Per aspera ad astra.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

It'd not works, link you posted shows OPA powering with +-9V.
Nothing wrong with a chip , it was design for:

"Single Supply Quad
Operational Amplifiers"
and they say:
"can operate at supply voltages as low as 3.0 V "


What is an error?
You have to change a circuitry when you powering single supply.
+input of the OPA has to be biased to half  of power voltage, one more resistor 100kOhm required
to be connected between +input and +5V
And capacitor in the negative feedback, would be helpful to prevent HF osculation.

 
Logged

Connecticut
Offline Offline
Edison Member
*
Karma: 17
Posts: 1216
RTFD (Datasheet in our case)
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

But the 100k resistor didn't work- It just made the output REALLY soft. I'll just do dual supply.

And where should I put the HF cap?
« Last Edit: March 06, 2011, 02:12:57 pm by baum » Logged

Montreal
Offline Offline
Faraday Member
**
Karma: 29
Posts: 2590
Per aspera ad astra.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

http://www.vellemanusa.com/downloads/0/minikits/manuals/manual_mk136.pdf
http://www.vellemanusa.com/us/enu/product/view/?id=351278

Cheers.
Logged

Connecticut
Offline Offline
Edison Member
*
Karma: 17
Posts: 1216
RTFD (Datasheet in our case)
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I'll try that... Thanks.

(The circuit mentions an "8E2" resistor, is this 8x10^2, or 800Ω
Logged

Montreal
Offline Offline
Faraday Member
**
Karma: 29
Posts: 2590
Per aspera ad astra.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

It's 8.2 Ohm, my opinion, it's not necessary, as IC 5532 has overdrive (shorting output) protection.
For LM324 , the same:
• Short Circuited Protected Outputs

Logged

Connecticut
Offline Offline
Edison Member
*
Karma: 17
Posts: 1216
RTFD (Datasheet in our case)
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

OK. Now I built my split power supply, and it works! But, if I am not grounded, there is this annoying low buzz. When I am grounded (touching long wire, metal table, any large metal object, it is crystal clear. Any ideas?

Thanks for all the help so far! How I can spy of people!
Logged

Connecticut
Offline Offline
Edison Member
*
Karma: 17
Posts: 1216
RTFD (Datasheet in our case)
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

*now

Sorry.
Logged

Pages: [1]   Go Up
Jump to: