# Wien Bridge Oscillator Problem

Discussion in 'Homework Help' started by Volt, Apr 21, 2010.

1. ### Volt Thread Starter Member

Nov 28, 2008
24
0
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

2. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
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.

3. ### Volt Thread Starter Member

Nov 28, 2008
24
0
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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4. ### JoeJester AAC Fanatic!

Apr 26, 2005
3,393
1,211
Is your ideal model actually the 741 model?

Last edited: Apr 21, 2010

Apr 20, 2004
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6. ### Volt Thread Starter Member

Nov 28, 2008
24
0
My ideal model is the virtual amplifier on Multisim

Apr 14, 2010
377
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Dec 5, 2009
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9. ### kingdano Member

Apr 14, 2010
377
19
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.