1. ECL Design Laboratory John Jakabosky – EECS 713

2. Goals & Deliverables Design an ECL laboratory exercise to give a participant an understanding of the operating principles of ECL Simulate the operation of the differential current amplifier at the core of the ECL OR/NOR gate Give participant pre and post-lab work to facilitate understanding

3. ECL Refresher ECL is a form of logic that uses npn BJTs At the core of the design is a differential current amplifier Trades high static power consumption for fast operation Outputs must be terminated Power supplies use negative voltages Produces less EMI and is more secure (from cryptographic side-channel attacks)

4. Differential Amplifier Two N type transistors with coupled emitters All current is shared between I 1 and I 2 v 2 is a reference voltage if v 1 > v 2 then current I 2 is small and v out is higher Otherwise v out is high The opposite effect is seen on I 1 path Easily exploited to provide OR/NOR logic

5. Pre-lab work Recommend watching NPTEL youtube Lecture 18 on Basic ECL Operation http://www.youtube.com/watch?v=MqidrO1TPvQhttp://www.youtube.com/watch?v=MqidrO1TPvQ Intro video provides Study the example schematic to be implemented

6. Lab Assignment Use PSPICE NPN Q breakout transistor model, set forward β=25 Design a PSPICE schematic based on the one provided Use 4mA current source, 250 ohm amplifier resistors -1.3 V reference, -5.2 V for VEE, 50 ohm input termination Determine current flow through R4 and R7 for a range of input voltages to 1 transistor input Set one input transistor to logic low (to demonstrate OR/NOR) sweep input voltage from -5.2V to 0V Provide PSPICE simulated current values

7. Current vs input Voltage

8. Post-Lab Work Determine power consumption estimate of differential amplifier resistors and BJTs Questions for participant Could additional transistors be used to convert current amplifier to output stage? Yes, one additional BJT for each output At what input voltage does the current flip from one path to the other? 1.3V or VREF Why is there a reduction in current flow at higher input voltages? The BJT have been forced into saturation Why might this design be faster than CMOS? Low input/output capacitance

9. References http://www.youtube.com/watch?v=MqidrO1TPvQ http://www.youtube.com/watch?v=BV-2gxFuAH0 http://en.wikipedia.org/wiki/File:ECL.svg http://en.wikibooks.org/wiki/Circuit_Idea/Revealing_the_Trut h_about_ECL_Circuits http://en.wikibooks.org/wiki/Circuit_Idea/Revealing_the_Trut h_about_ECL_Circuits http://www.engr.colostate.edu/ECE562/Pspicetutorial.pdf http://www.ece.mcmaster.ca/faculty/bakr/ece2ei5/PSpice_Ex periment.pdf http://www.ece.mcmaster.ca/faculty/bakr/ece2ei5/PSpice_Ex periment.pdf http://www.st- andrews.ac.uk/~www_pa/Scots_Guide/audio/part1/page3.ht ml http://www.st- andrews.ac.uk/~www_pa/Scots_Guide/audio/part1/page3.ht ml http://johncohn.org/base/2012/10/11/thursday-morning- history-of-computing/ http://johncohn.org/base/2012/10/11/thursday-morning- history-of-computing/

10. Questions? Discrete ECL board from IBM Console