1 / 35

CS8421-9-13-2006

CS8421-9-13-2006. Transistor/Gate Experiments. CS8421 Computing Systems Dr. Ken Hoganson. Class Will Start Momentarily…. 3-Input AND from Transistors. Illustrates basic use of IDL-800 Illustrates construction of gates

isaac-solomon
Download Presentation

CS8421-9-13-2006

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CS8421-9-13-2006 Transistor/Gate Experiments CS8421 Computing Systems Dr. Ken Hoganson • Class • Will • Start • Momentarily…

  2. 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.

  3. Transistors in Series V+ A B C Out • Construction of 3-Input (A,B,C) AND from transistors. • Note the resistor and output are at the “bottom”. • Three inputs (from switches)

  4. Connection to Power V+ A B C Out + 5 volt power supply. Connects to top transistor Next slide shows the connection to power.

  5. Connection to Ground V+ A B C Out After the output. Through the current-limiting resistor.

  6. Connection to Logic Switches V+ A B C Out • Switches connect to each transistor. • Switches are either: • 0-off, no voltage, • or • 1-On, +5 volts

  7. Measuring Output with the Meter V+ A B C Out 2.13 • Digital Volt Meter connects to output, and to the ground. • It measures the voltage differential between those two points.

  8. 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.

  9. Voltage – 1 input on V+ A B C Out 2.13 Illustrates the “transistor bleed-through” effect.

  10. Voltage – 2 inputs on V+ A B C Out 2.84 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.

  11. Voltage 3 inputs on V+ A B C Out 4.07

  12. “Bleed-Through” voltage can light a LED, and be detected as a “1” V+ A B C Out 2.83 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.

  13. 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

  14. NAND gate V+ A V+ B Out A C B Out C • Changing the location for sampling output voltage reverses the operation. • Relocate the current limiting resistor. AND NAND

  15. Close-up of transistors in series, with: • Output ahead of the transistors • Current-limiting resistor • Three input wires from switches

  16. Close-up of switches • One switch for each transistor base

  17. Connection to DVM and LED • Note, that the output is high (4.69v) • And, the LED is “ON”

  18. No problem with “Transistor Bleed-Though” • Note that two switches are ON. • With the AND, this produces a 2.8v output.

  19. No problem with “Transistor Bleed-Though” • Note that two switches are ON. • With the AND, this produces a 2.8v output, or an incorrect “1” for the AND. • Here, it produces a clear “1” at 4.7v, and lights the LED, correct for a NAND.

  20. Note that all three switches are now ON.

  21. Note that all three switches are now ON. • With the NAND, the output is a “0”, at 0.06v, and the LED is OFF. • Note the large voltage difference between a “0” at 0.06v, and a “1” at 4.69v: a differential of 4.63v • The voltage differential for the AND is only 4.07-2.87=1.2v

  22. Caution Do not connect inputs A, B, or C directly to the 5v power supply, as there is no current-limiting resistor between the inputs and ground. The logic switches on the IDL-800 are “conditioned” to control their response. In actuality, the inputs to a logic gate, are generally other logic devices, and are NOT directly connected to the power supply (see diagram). Note that there are other implementations of logic gates, using different technologies, using less current, lower voltages, and switching faster. V+ V+ Out A B C

  23. End of Lecture End Of Today’s Lecture.

  24. Blank Slide

More Related