Article View: sci.electronics
Article #8517Re: Switched Filters
From: Joe Keane
Date: Thu, 22 Nov 1990 00:37
Date: Thu, 22 Nov 1990 00:37
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1371 bytes
In article <17100009@inmet> erich@inmet.inmet.com writes: > in ______./ .______/\/\/\_______ out > switch res | > | |cap > | | > | > ____ > /// >Will Output Signal = Input signal x Duty cycle of control line > with no distortion of the output signal relative to the input > except for attenuation? Almost. The problem is that you're not really switching voltages, since when the switch is off the filter input is disconnected rather than grounded. The output will just follow the input. If you switch the filter input to ground during this time, the circuit will behave as you expect. It's easier to work with current switching and filtering, since when you open the switch you know you'll get zero current. In this case your energy storage device will be an inductor rather than a capacitor. This is how most switching power supplies work.
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arc1-ca.pugleaf.net!utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!vsi1!indetech!pacbell!osc!jgkReferences:
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Path: arc1-ca.pugleaf.net!utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!vsi1!indetech!pacbell!osc!jgk From: jgk@osc.COM (Joe Keane) Newsgroups: sci.electronics Subject: Re: Switched Filters Summary: Keep filter input impedenance fixed. Message-ID: <4028@osc.COM> Date: 22 Nov 90 00:37:18 GMT References: <17100009@inmet> Reply-To: jgk@osc.COM (Joe Keane) Organization: Versant Object Technology, Menlo Park, CA Lines: 22