# Using capacitors in bridge t-type

Discussion in 'General Electronics Discussion' started by pump, Mar 15, 2012.

1. ### pump

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Nov 4, 2011
Hope somebody could help me explain this from the circuit below.....What effect do the capacitors have?

Last edited: Mar 16, 2012
2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,497
2,839
Jan 21, 2010
You may have to try posting the image or link again...

3. ### pump

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Nov 4, 2011
Thanks will try again

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4. ### pump

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Nov 4, 2011
Not sure but my first thought is that the configuration will only attenuate under a certian frequency. If over this frequency then te signal will not get attenuated?

Is that correct?

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Nov 4, 2011
BUMP

6. ### poor mystic

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Apr 8, 2011
The circuit looks incomplete to me; I think that in order to understand it you need to consider the load, which will be most easily modelled as a pure resistance across the right hand side of the circuit.
Now we see that the capacitors are in series with the load, so that they have a "high pass" characteristic.

7. ### pump

24
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Nov 4, 2011

Yes that circuit is incomplete I removed the load just for the picture. So my thoughts were correct. At high frequency the input signal will not be attenuated?

8. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,497
2,839
Jan 21, 2010
As has been suggested, the load is all-important.

If the impedance of the load is high enough, the circuit won't attenuate anything at all.

The lower the load impedance the lower the frequency the 3db point moves.

9. ### Laplace

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184
Apr 4, 2010
My analysis of the circuit is in the attachment. The node equations are on the first line. These are manipulated into a transfer function of the form, 20log(Vout/Vin). For the graph, component values selected have Rp=Rl so for very low frequency or DC input, Vo/Vi=0.5 or 6dB. Very high input frequency passes through the capacitors without attenuation, or 0dB. The depth of the notch seems to be related to the value of Rt.

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10. ### pump

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Nov 4, 2011
Laplace thank you for the explaination. Thats quite a bit of work you have put in there

Thank you all for helping me understand this circuit. Sometimes reserching by yourslef isn't enough, by speaking to people like yousleves and having it explained in plain English is whats needed. Thanks again for all your help

Last edited: Mar 17, 2012