All Forums  Electronics  Other Circuits  Calculating frequencies for Spectrum Analyzer

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Screensize: 640 x 480 800 x 600 1024 x 768 1280 x 1024 UserName: Password: Format Mode: Basic  Help  Prompt  Format: Font Andale Mono Arial Arial Black Book Antiqua Century Gothic Comic Sans MS Courier New Georgia Impact Lucida Console Script MT Bold Stencil Tahoma Times New Roman Trebuchet MS Verdana   Size 1 2 3 4 5 6   Color Black Red Yellow Pink Green Orange Purple Blue Beige Brown Teal Navy Maroon LimeGreen Message: * HTML is OFF * Forum Code is ON Smilies [quote][i]Originally posted by audioguru[/i] [br]The project uses an odd LM3900 quad amplifier IC and a Japanese LED driver that is obsolete. The filters are not gyrator but are called Multiple Feedback Bandpass Filter and the calculation of parts and frequency are shown in Google. The bandpass is wrong for a spectrum analyser since the peak is narrow-band and the simple skirts are gradual and wide-band. A spectrum analyser needs filters with a response that has a flat amplitude for its bandpass then sharp skirts. Here is a simulation of the response of a Multiple Feedback Bandpass Filter: [b]Download Attachment:[/b] [url="./uploaded/Audioguru/201451211543_multiple feedback bandpass filter response.PNG"][img]./icon_paperclip.gif[/img] multiple feedback bandpass filter response.PNG[/url][br]26.44 KB [img]./uploaded/Audioguru/201451211543_multiple feedback bandpass filter response.PNG[/img] [/quote]    Insert an Image File (GIF, JPG, JPEG, BMP, ZIP, PNG) Check here to include your profile signature.