impedance matching for LT6202 op amp and LPF

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robismyname

Joined: 17 Jan 2008
Posts: 163
Helped: 2
Location: Central Florida

25 Oct 2009 5:26 LT6202 op amp and LPF

I want to place a low pass 5-pole Butterworth filter on the input of the op amp (non inverting). Do I need to worry about the issue of impedance matching the filter with the opamp? What is the impedance of the op amp?

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kspalla

Joined: 19 Aug 2008
Posts: 849
Helped: 140

30 Oct 2009 5:43 Re: impedance matching for LT6202 op amp and LPF

Quote:

Do I need to worry about the issue of impedance matching the filter with the opamp?

Theoretically one need to consider the impedance of both input and output sides.
As the output of filter ( normally 50 or 75 ohm) is much much smaller than the input impedance( few Mega Ohms), we can neglect the part of impedance matching.
However for this kind of filter there should be shunt element/s to match the impedance.

Quote:

What is the impedance of the op amp?

Theoretically infinite.