# Category: The Filter Wizard Remastered

## An appendix to Filter Wizard #14 (“Match Point”)

Designing a filter using a spreadsheet. No sophisticated charts, no pole zero relationships, determination of a response type, none of those overly complex equations I learned in Continue Reading...

## Bruton Charisma: Make Those Inductors Vanish Using Savvy Scaling

We set out to eliminate the inductors in our LC lowpass filter – and ended up doubling the number of them! We’ll see shortly just how these can be made to disappear in one mathematical Continue Reading...

## Dualling Master: Swap Current and Voltage for Easier Filter Design

Using optimization to design circuits (some might call it organized guesswork – for some algorithms, that’s a pretty good description) isn’t a new Continue Reading...

## Match Point: Why Maximum Power means Minimum Sensitivity

You have a sinewave signal generator with a (resistive) 50 ohm output impedance, and it can produce 1 Vrms into an open circuit. Your customer has given you a black box with an input impedance of 3.3 kohm, and for it to function correctly, it requires an input Continue Reading...

## Filter Design using the “Million Monkeys Method”

There’s a further cool thing you can do with a spreadsheet that most SPICEs can’t. That’s to use the spreadsheet ‘solver’ functionality to adjust component values in the search for a better-fitting circuit – or even to find a set of component Continue Reading...

You now need to adjust component values to achieve some system goal, such as predefined frequency response or time behaviour, and there’s no closed method for working out those Continue Reading...

## Excel Tunes Up your Schematic Files

In previous posts I’ve talked about transferring spreadsheet-based circuit design “directly” to the lovely LTspice simulator, and a reader of The Filter Wizard was keen to understand exactly what “directly” actually meant, and to get some practical Continue Reading...

## Fainting in Coils

The required selectivity of a customer design implied four-pole filters with about 10% bandwidth (passband width about 10% of the centre frequency). There was a catch---a tight power Continue Reading...

## Countdown to s-to-z…

Now, our customer doesn’t want to buy big, expensive, high quality capacitors to build an active filter with this response. So, having established the principle of optimizing in the analogue domain, let’s look at whether need to make any changes in order Continue Reading...