The first digital systems was based on
relays and valves (tubes) - the power disparaged and the cost was huge.
Next generation of logic, from the 1950ies, was
based on the new Bipolar Junction Transistor. (RTL and
The invention of the integrated circuit (IC)
started the next revolution in the world of digital design.
Through the 1960ies was a family of digital components (the
74xx/54xx series) developed. The components became more complex
(and expensive) until the invention of the first integrated CPU
(i4004) started the next revolution.
A disadvantage by TTL is the power consumption - a
BJT need a current in order to be turned ON.
The first MOS transistor was developed back in
1960, However was it first in the 1970ies this technology became
popular for integrated circuit.
The introduction of CMOS technology in the 1980ies
made it possible to develop very complex high-speed integrated
circuits. The Power consumption follows the formula.
of CMOS logic
= Constant * Frequency * Voltage 2
which depends mostly on the physics of the chip (die)
- The capacity of the gates - switch times, internal
the crystal frequency of the system (Bits of a binary
counter doesn't change with the same frequency)
real "killer" and hence lots of effort made to reduce this
(to say 1.5 Volts)
historical facts can be found here