3 input and from transistors
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3-Input AND from Transistors. Illustrates basic use of IDL-800 Illustrates construction of gates Illustrates the “transistor bleed-through” problem that affects the AND circuit. V+. A. B. C. Out. Transistors in Series. Construction of 3-Input (A,B,C) AND from transistors.

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3-Input AND from Transistors

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3 input and from transistors

3-Input AND from Transistors

  • Illustrates basic use of IDL-800

  • Illustrates construction of gates

  • Illustrates the “transistor bleed-through” problem that affects the AND circuit.


Transistors in series

V+

A

B

C

Out

Transistors in Series

  • Construction of 3-Input (A,B,C) AND from transistors.

  • Note the resistor and output are at the “bottom”.

  • Three inputs (from switches)


Connection to power

V+

A

B

C

Out

Connection to Power

Next slide shows the connection to power.

+ 5 volt power supply.

Connects to top transistor


Connection to ground

V+

A

B

C

Out

Connection to Ground

After output.

Through the current-limiting resistor.


Connection to logic switches

V+

A

B

C

Out

Connection to Logic Switches

  • Switches connect to each transitor.

  • Switches are either:

    • 0-off, no voltage,

    • or 1-On, +5 volts


Measuring output with the meter

V+

A

B

C

Out

2.13

Measuring Output with the Meter

  • Digital Volt Meter connects to output, and to the ground.

  • It measures the voltage differential between those two points.


Measuring output with a led

Measuring Output with a LED

The output can be connected to a Light Emitting Diode (LED) rather than to the DVM.

A voltage of around 2.5 and greater will cause the LED to light.

The LED is already wired on one end to the ground.

A current limiting resistor ensure that the LED does not receive too great a voltage and current.


Voltage 1 input on

V+

A

B

C

Out

2.13

Voltage – 1 input on

Illustrates the “transistor bleed-through” effect.


Voltage 2 inputs on

V+

A

B

C

Out

2.84

Voltage – 2 inputs on

Illustrates the “transistor bleed-through” effect.

Two transistors, larger voltage detected.

This voltage is large enough to be detected as a “1” by the LED.


Voltage 3 inputs on

V+

A

B

C

Out

4.07

Voltage 3 inputs on


Bleed through voltage can light an led and be detected as a 1

V+

A

B

C

Out

2.83

“Bleed-Through” voltage can light an LED, and be detected as a “1”

Illustrates the “transistor bleed-through” effect.

Two transistors, larger voltage detected.

This voltage is large enough to be detected as a “1” by the LED.


Use nands or nors

Use NANDs or NORs

  • Need to support AND, OR and NOT as Boolean operations

  • Manufacturing cost:

    • Single silicon layering

      • don’t need to support two places (layers) to connect resistors, or measure output

      • AND/OR different layer from NOT

    • Complete set of operations – NAND or NOR can be wired for any logic

      • Fabricate a chip with one type of gate

  • Avoids AND “transistor bleed-through” problem

  • Actual modern logic implementations will vary as technologies evolve


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