Using Cause and Effect Relationships

By the mid-1990s, I had already developed my own philosophy about electronic circuits, and I decided it was time to share it with my colleagues. In the spring of 1997, I presented a series of three papers at the XXXII Scientific Conference on Communication, Electronic and Computer Systems at the Technical University of Sofia. The first of these was devoted to my heuristic course on analog circuits, in which I had implemented my circuit philosophy. There I shared my idea of using cause and effect relationships for the purposes of understanding, presenting and inventing  circuits. In this post, I will tell you about this venture of mine.

Revealing causality

As a rule, classil electronics courses do not reveal ''cause and effect relations'' in electronic circuits. For example, who cares if there is a causality and what causes what (what quantity is an input and what an output) in Ohm's law? Authors just suppose that voltage and current change simultaneously; they do not mind how the famous rule is written (I = V/R, V = I.R or R = V/I).

Only, we human beings consider every change in this world as a result of some cause (in electronics that means the output quantity is a result of the input one). We cannot imagine that the input and output quantities can change simultaneously. We know that always the input is first and the output is second; so, the output always follows (delays) the input.

Introducing causality

In the case when apparently there is no causality in electronic circuits, we can introduce it. Let's for concreteness consider the example above of Ohm's law. There, we first assume that ''voltage causes current'' (I = V/R) in a voltage supplied Ohm's circuit; thus we "invent" the simplest [[Circuit Idea/Passive Voltage-to-Current Converter|voltage-to-current converter]].

Changing causality

But we know that this cause and effect relation is an arbitrary choice; so, we can change (reverse) it. This means we can assume with the same success that ''current causes voltage'' (V = I.R) in a current supplied Ohm's circuit; thus we "invent" the reverse current-to-voltage converter.

Evolving this powerful idea we will (re)invent a lot of useful and original circuits by using any accessible ''circuit points'' (including circuit outputs, supply terminals, etc.) and ''component parameters'' as an input. For example, varying with resistance as an input quantity we will obtain a ''resistance-to-current'' converter'' (in the case of a voltage supplied Ohm's circuit) and a'' resistance-to-voltage converter (in the case of a current supplied Ohm's circuit). Then, applying an input voltage to the output of an emitter follower we will "invent" the odd ''common-base transistor amplifying stage''. Later, changing causality, we will transmute a digital-to-analog converter into a ''digital controlled amplifier''.

Web resources

Using Cause and Effect Relationships (seeing, introducing and changing the causality in circuits; Circuit Idea wikibook)