# Why do people state their circuit uses <insert> transistors?

I'm pretty new to circuits, and still don't know exactly how transistors work, but when I search up a tutorial for circuits that include Transistors, they all have in the title, "One Transistor This", "One Transistor That".

Is there any specific reasoning behind that?
What is so special about Transistors?
Why not include "2 Capacitors"?

Example, I searched up "One Transistor FM Receiver", I know that's a little cheaty, but WHY do all these video's have it in the titles?

• "but WHY do all these video's have it in the titles?" - Because that's the way Google works ;-) Dec 26 '14 at 6:27
• @RogerRowland Maybe I'm not explaining it well enough. Why do people bother putting it in the title? What is so special about it?
– user62118
Dec 26 '14 at 6:29
• Finn - when you want to find a tutorial for transistors (how they work) - why don`t you use the keyword "tutorial"? Searching for "one transistor" primarily you will find complete circuits which work with one single transistor only.
– LvW
Dec 26 '14 at 8:51
• The number of "active devices" is an indication of the circuit complexity. It was not that unusual to see transistor count on IC datasheets, for example. Dec 26 '14 at 9:42
• @SpehroPefhany, I'm pretty sure transistor counts were included in datasheets to allow certain customers (ones doing designs for military equipment?) to do reliability estimates according to some standardized methods. Dec 26 '14 at 18:09

Once upon a time, transistors were likely to be the most expensive part in a simple amplifier or oscillator design. Even today, a discrete transistor is likely to be 2 to 10 times as expensive as a discrete resistor or capacitor.

So a "one transistor" circuit was roughly half as expensive to build as a "two transistor" circuit. And cost was an important reason to prefer circuits with fewer transistors.

• Ar-hah. Quick eBay search. $1-20 for ONE transistor. And I can buy 200 resistors for$1!?!? Wow.
– user62118
Dec 26 '14 at 6:44
• If you buy transistors 200 at a time, you might get them for \$0.05 each, but they'll still be substantially more than resistors or capacitors. Nowadays coils might be priced comparably to transistors so the transistor cost doesn't necessarily totally dominate the design cost. But the number of transistors still gives a rough idea of the design complexity. Dec 26 '14 at 6:54
• Yes. I understand @ThePhoton. It just bugged me seeing all the Transistor this, Transistor that stuff. :P
– user62118
Dec 26 '14 at 7:16
• I believe the same applies to "one chip" or "one jellybean chip" over "two chips" or "one ASIC". Dec 26 '14 at 7:20
• Goes back a little further than that, to when the active devices were even more expensive and precious... vcomp.co.uk/one_tube_1935/one_tube_1935.htm Transistor circuit designers simply inherited the practice... Dec 26 '14 at 10:34