# Square wave oscillator help please.

Discussion in 'Electronic Basics' started by John Popelish, Jul 25, 2004.

1. ### John PopelishGuest

Sorry, I cant find any reference to a square wave oscillator on this
page.

2. ### Jonathan KirwanGuest

If you download the datasheet in PDF form, then it's in the bottom right corner
on page 5 of the amplifier datasheet.

Jon

3. ### John PopelishGuest

Thank you. Adjust the size of the capacitors by 1/40.

4. ### Animesh MauryaGuest

It's on the datasheet (page 5) http://www.national.com/ds/LM/LM386.pdf

Best regards,
AM

5. ### Animesh MauryaGuest

You are probably looking for this, time period of square waves is

T=2*RC*In((2R1 + R2)/R2)

Where in the original schematic
R=30k, C=.1u, R1=1k and R2=10k

Adjust these values which suit you the best.

Best regards,
AM

6. ### RubiconGuest

Hello,

Can anyone help me change this LM386 1kHz square wave oscillator to
40kHz? Formulas or a walk through?
PDF Page 5 http://www.national.com/pf/LM/LM386.html

There's nothing that I can find in the PDF to help me and searching
has found mainly square wave or amplifier kitsets.

Regards,

Andrew.

7. ### RubiconGuest

Thankyou for the help.

I apologise for not being specific enough, it's something I must
attend to.

Regards,

Andrew.

8. ### RubiconGuest

So:

0.1uf / 40 = 0.0025uF
50uF / 40 = 1.25uF

Both non standard values in my catalogues. Time to work out parallel
caps?

0.0015uF + 0.001uF = 0.0025uF
1uF + 0.15uF + 0.1uF = 1.25uF

I thought the LM386 might make a better ultrasonic transducer driver
than the 555 astable circuit I have but it seems a little messy in
comparason.

Regards,

Andrew.

9. ### RubiconGuest

Thanks.

Though mathematics was never my strong suit I can work through that