Wien Bridge Oscillator Problem

V

Thread Starter

Volt

Joined Nov 28, 2008

24

Apr 21, 2010

• #1

Hi, I need to design a wien bridge oscillator with a frequency of 20kHz, the values for the resistors and capacitors in the tuned network i've calculated are 500 ohms, and 16nF. However when I simulate this the frequency of the oscillations is 16kHz.

I don't know why this is, can anyone explain this and help get the right frequency.

thanks

 

Wendy

Joined Mar 24, 2008

23,809

Apr 21, 2010

• #2

Have you taken the input impedance of the amplifier into account?

Seriously, we need a schematic, there is no way we can even begin to help due to lack of information.

 

V

Thread Starter

Volt

Joined Nov 28, 2008

24

Apr 21, 2010

• #3

Hi,

I'm simulating with an ideal op amp so I suppose the impedance isn't an issue.

I have attached the schematic, on the frequency selective components:

R1=R2= 500Ω
C1=C2=16nF

I work that out to be:

1/((2pi)(500Ω)(16nF) ≈ 20 kHz

but it is only simulating to 16kHz.

The other component values:

R3=18.2 kΩ
R4= 10 kΩ
R5= 5kΩ


Thanks

 

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JoeJester

Joined Apr 26, 2005

4,390

Apr 21, 2010

• #4

Is your ideal model actually the 741 model?

 

Last edited: Apr 21, 2010

beenthere

Joined Apr 20, 2004

15,819

Apr 21, 2010

• #5

TI's article might help - www.ti.com/sc/docs/apps/msp/journal/aug2000/aug_07.pdf

 

V

Thread Starter

Volt

Joined Nov 28, 2008

24

Apr 21, 2010

• #6

JoeJester said:

Is your ideal model actually the 741 model?

Click to expand...

My ideal model is the virtual amplifier on Multisim

 

K

kingdano

Joined Apr 14, 2010

377

Apr 21, 2010

• #7

beenthere said:

TI's article might help - www.ti.com/sc/docs/apps/msp/journal/aug2000/aug_07.pdf

Click to expand...

your link is broken!

has allaboutcircuits.com before the ti link.

 

retched

Joined Dec 5, 2009

5,207

Apr 21, 2010

• #8

fix -
www.ti.com/sc/docs/apps/msp/journal/aug2000/aug_07.pdf

 

K

kingdano

Joined Apr 14, 2010

377

Apr 21, 2010

• #9

cool app note

i see a useful circuit i can build at work

an encoder simulator - quadrature oscillator into a schmitt trigger or other sine to square wave converter.

then i can use that signal to drive fet gates to switch on 12V or 24V to the inputs of our printers.

i think they need 24V...will check tomorrow.

might help me prove my knowledge of analog...thank you app notes.