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Anyone in the synthetic biology community is welcome to attend.

Wednesday at 1pm 32-D463, MIT ***NOTE ROOM CHANGE***

Topic of discussion

Tom Knight will be giving an introduction to different electronics device families and their specifications. This introduction should help to frame future lunch discussions regarding specification of biological device families.


Please list your name below if you are attending so that we order enough food. (To add your name to the list, type #~~~~.)

  1. Reshma 14:29, 20 September 2006 (EDT)
  2. bruno 18:32, 22 September 2006 (EDT).
  3. Ilya 18:46, 22 September 2006 (EDT)
  4. David 23:56, 22 September 2006 (EDT)
  5. Austin Che 13:38, 23 September 2006 (EDT)
  6. Caroline10:26, 25 September 2006 (EDT)
  7. tk 13:09, 25 September 2006 (EDT)
  8. Endy 13:26, 25 September 2006 (EDT)
  9. hkeller 13:42, 25 September 2006 (EDT)
  10. Jbuck 13:50, 25 September 2006 (EDT)
  11. cmc 14:01, 25 September 2006 (EDT)
  12. BC 15:29, 25 September 2006 (EDT)
  13. Timp0 17:03, 25 September 2006 (EDT)
  14. Samantha 19:47, 25 September 2006 (EDT)
  15. Jason Kelly
  16. Julie Norville
  17. PatrickBoyle 11:09, 26 September 2006 (EDT)
  18. JeremyZucker 19:16, 26 September 2006 (EDT)
  19. Ken Oye
  20. Jake Beal


(by Reshma Shetty, feel free to modify)

Logic devices

  1. Performs logical operation
  2. Power gain and signal restoration

These two functions are often combined but don't necessarily need to be.

History of logic device families

RTL (resistor transistor logic) family

  • First integrated transistor family built on a single piece of silicon.
  • Resistor = logical operation
  • Transistor = signal restoration
  • didn't have perfect signal restoration
  • very slow
  • Tom drew a parts level diagram of a logic device. Depending on which resistor parts you chose, the device could either implement a NOR or NAND logic operation
  • very cheap which is why it took off

DTL (diode transistor logic) family

  • uses diodes instead
  • more robust control over voltage
  • also very slow
  • Motorola

TTL (transistor transistor logic) family

  • faster
  • push-pull
  • has standard power supply voltages and interfaces. Therefore, you could transition from one series to another. The series differed in speed and power dissipation.
  • Texas Instruments

CMOS transistors

  • made from P-MOS and N-MOS transistors
  • P-MOS transistors are naturally inverting
  • logic swings go from ground to positive power supply unlike previous logic families ... bigger swing.
  • RCA

Device families

Transitions from one family to another were driven by performance requirements and the technology. Transitions between device families were accompanied by transitions in related technologies like the power supply.

How do you cope with poor signal restoration?

  • vary power supply voltage to change noise margins
  • it was hard to do good designs in RTL devices

Fanout (~10 max)

  • Determined by the physical limitations of the device. It is not driven by the applications.

Fanin (~8 max)

  • Determined by how many inputs the device is designed to take in.

Wire-OR: a type of logic that may be important in biology

  • can do two stages of logic out of a single gate
  • have open collector gates
  • similar to letting a protein be expressed in either of two different ways

Also see relevant papers on noise margins. How do you design reliable logic circuits? Gotten a lot of attention over the years. A lot of this complexity is hidden from the users.