Square wave oscillator help please.

[John Popelish]

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.

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

 

[Jonathan Kirwan]

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

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

Jon

 

[John Popelish]

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

Jon

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

 

[Animesh Maurya]

Rubicon wrote:

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

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

Best regards,
AM

 

[Animesh Maurya]

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.

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

 

[Rubicon]

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.

 

[Rubicon]

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

Thankyou for the help.

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

Regards,

Andrew.

 

[Rubicon]

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.

 

[Rubicon]

Thanks.

Though mathematics was never my strong suit I can work through that
formula with the 1kHz/circuit values example to start with.

Andrew.