M1955-1980-Transistors

1955-1980 Transistors

  

 

 

 

 

 

 

 

    

 

 

 

   

 

Logic Devices

 

After WW II interest increased interest in making logic devices.  IBM, and others, made Logic cards and semi-conductor firms made families of integrated circuit devices as:  RL (resistor logic), DL (diode logic) and RTL (resistor transistor logic) and Emitter coupled logic. These were marketed in the Dual Inline packages.  

 

IBM Flip Flop on a plug in card

Logic Elements   A logic device is a gate.    Below is a TTL NAND gate  with Truth Table.

  

           TTL NAND gate                       Diagrammatically it looks like this                        invert NAND and you have AND:

When A and B are both High or 1's the output for this device of A+B is low or 0.  Since it requires A and B to be  l for an output 0 the AND logic produces 0 the inverse of 1 or Not 1 so the device is called a Not AND or NAND. The addition of a small circle on the nose of the symbol indicates the AND output is the inverted to a NAND,  A line above a letter indicates the inverse; the line above A+B defines it a “not”.

 

These became widely used standard terminologies, with Truth Tables defining the possible conditions.

 

Boolean Addition, Multiplication and complementation

 

   

            Packaging took on various forms, with plastic encased dual inline the most common with ceramic packages considered better.  The most common were 14 pin then 16 pin packages, with more pins for complex functions.  Packages had it’s own terminology.  Pins numbering started with zero.  The terminologies were similar but different depending on the kind.  Bi-polar power pins were always Vcc and Grd,   CMOS power pins were Vdd  and Vss ; as shown above.

  

Ladies in clean rooms bond chips to frames with gold wires

 

A Flip Flop  is a single bit programmable memory.

 

Clocked  S-R (set reset) Flip Flop made from logic devices

O for Output was called Q, to not confuse with zero.  The inverse of Q is Not Q (a line above Q)

CMOS (Complementary Metal Oxide Semiconductor)

            The Personal computer revolution began when the semiconductor industry achieved greater photo resolution and when CMOS (Complementary Metal Oxide Semiconductor) technology; was developed making it possible to include more transistors on a chip and run cool. Arithmetic processing had gone from 1 to 4 bits to 8 bits using TTL (Transistor to Transistor Logic) technology, however TTL consumed too much power.  A bipolar transistor, as use in TTL (transistor to transistor logic), must flow current from the input to the output in order to cause the transistor to be “on”. MOS transistors are commanded by an electrical charge, there is nil command current flow.  when more transistors were added, the devices would get hot. TTL was widely used for logic but computer use was limited to main frames which could be water cooled. CMOS uses two “complementary” transistors between high and low power; one is off when the other is on, with CMOS no current flow except for the instant when both transistors are changing state. This greatly reduced heat load which permitted placing many 8 bit registers on the same chip, improve the ability to perform arithmetic, and implement a variety of programmable logic functions. Software could be written in the microprocessors family of built in “machine code” functions.

 

 

TTL                vs       CMOS   Inverter                                                   NOR gate & Truth table

            CMOS transistors were soon combined to invert signals and perform logic functions. A standard logic family was: AND, NAND, OR, NOR, EXCL-OR & EXCL-NOR gates. For a AND gate  1 and 1 produce a 1 output. For a  NAND  1 AND 1 produce a 0 output, ie “not” like an AND. Truth tables are, where input A and B produce output Q.  The “output” was designated Q, rather than O to preclude confusion between letter O and number 0

Family of Truth Tables

A

B

Q

Q

Q

Q

Q

Q

0

0

0

1

0

1

0

1

0

1

0

1

1

0

1

0

1

0

0

1

1

0

1

0

1

1

1

0

1

0

0

1

 

 

AND

NAND

OR

NOR

EXOR

EXNOR

Type  D Flip Flop & truth table plus Transmission Gate

The D Flip Flop became the building block for counters, shift registers, latches, etc. Sets of these in 14 and 16 pin Dual Inline packages swept the electronics industry like wildfire initially as TTL parts and then as CMOS parts.

The Transmission Gate was unique to CMOS and played a very important roll in many applications. For example by placing a P and N transistor in parallel, it could pass analog plus or minus signals – and the on/off command signal independent of the controlled signal.

          The Arithmetic Logic Unit (ALU) was the first step toward a microprocessor. The figure shows how it could be commanded to perform various arithmetic functions.

Arithmetic Logic Unit; paved the way to microprocessor