This is undoubtedly an oversimplification, but the nice thing about physics is they work whether you understand them or not. The resistors and capacitors are the filtering jazz, and the op-amp applies the gain. All right! Sallen-Key it is! The Filter Circuit The higher the order, the steeper the slope at the cutoff. I think that has to do with how intense the dropoff in amplitude is above or, in this case, below cutoff frequency. Also, it’s a second-order filter for those of you who are into that sort of thing. I also wanted an active filter so that it accounted for the drop in gain from the filtering part. The fact that they have so many uses makes them… well, useful. Things like eliminating mic stand rumbles, cleaning up vocals, or making distorted guitars layer nicely. High-pass filters can be used for lots of things. Anyway, I settled on a Sallen-Key high-pass filter to be my first attempt. I asked Peterson for suggestions as to what he thought might be a nice simple filter design to adapt for my first circuit, and he kept trying to tell me about some sort of Salad he’d been eating the other day, and something about having lost his keys-he’s always doing that- so no help there. I tried to think of what would be a useful circuit to have in the studio, and I came up with high-pass, and low-pass filters. Since I'm not an Electrical Engineer, and I really don't know what I'm doing, I wanted to start with something as simple as possible. That’s when, all of a sudden, months later, it hit me: I could use these to design my own Colours! I said, “Thanks, no thanks,” and finished my model. Then, one day, out of the blue, when Peterson caught me using them as banquet tables for a model of the QE2 I was constructing, he mentioned in passing that they could be used to design and prototype your own custom Colours. We have so many of those little white rectangles lying around, and before I knew what they were I had come up with plenty of alternative uses for them (coasters, Tarot Cards, etc). Designing Your Own Colours (Without Any Electronics Knowledge) So since I've been putting so many of these "Design Your Own Colour" boards in the Colour Palette kits, I’ve decided it’s about time I got my hands dirty with actually Designing My Own Colours. I’m a musician, I like origami, and I’ve been working here at DIYRE for 5 months (Peterson still won’t tell me what the letters stand for). I would have chosen a multiple feedback, it saves one resistor and handles Q better, but at 0.1 dB, it's fine as it is.Hi, my name is Chris. The gain is 2, the ripple ~0.1 dB, the corner frequency is at -3 dB, 500 Hz (usually considered the end of the passband for a Chebyshev). Here's your diagram with some annotations:Īlthough I've never seen this particular arrangement before, I'll argue that the above can be reduced to: The table of parameters for unity gain from your Analog Devices link and for giggles and kicks a Quad Op Amp's worth of an 8th order filter. Again you may scale up impedance to the RC values with the same product just for low current on CMOS type Op Amps. Here I used Falstad's Analog filter site and chose the -3dB BW = 500 Hz /1.93432 = 259 Hz and they only offer unity gain filter tools.but in higher order filters, usually you defined the Stop-Band attenuation and frequency with the Pass-Band gain or attenuation with frequency. In the other filter designs, you can choose the attenuation level where the phase has maximum linearity like -6 dB or -10 dB. This is important not to confuse the two bandwidth definitions as some may assume BW is always -3dB rather than the "Ripple BW" where the ratio varies depending on the order of the filter. Table 1.2 on p.2 shows the Ripple BW f to -3dB f for 0.1 dB ripple filter and only the 2nd order has the value 1.93432= f_ripple/f-3dB which supports my comment that for this filter when Ripple = 0 equals the Butterworth Filter at 1/2 the cutoff frequency. Your link shows the analytic approach only for a unity gain 0.1 dB normalized frequency response on page 9 This way takes a few minutes.ĥ00 Hz HPF 2nd order Chebychev response S&K filter Av=2 in passband = 6.02 dB +/- 0.1dB This is not what your Prof expects but it is how I would approach it.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |