IDEAS to INTEGRATED CIRCUITS

      LM13600_Die_Photo

  ========RESOURCES===================

  1) Cheat sheets for Analog IC Design
       An ongoing collection of  Cheat Sheets.
       Details that have been critical to past IC designs.

  2 )  Frequently Used Javascript Calculators 
        Some times it is far easier to just create yourself a tool in order to save a lot of work.
     A) Recording Reverse Polish calculator
     B) R_C_F calculator
     C) R_C_L_F calculator
     D)
Javascript Calculators

  3)   Templates for Cut and paste
        Getting something to work often requires far more attention to detail than the help files provide.

======INTEGRATED_CIRCUIT_LESSONS==========

  1) Development of the LM13600/LM13700    
           Above is a Photo  of the LM13600/13700 STEREO Transconductance Amplifier.
          In the 70's , a different thickness of oxide, would appear in bright colors under the microscope.

  2) Ground Fault Interrupter Lessons
       
When lasted looked, about 50% of  market uses this
  ground fault interrupter.

  3) Processing Development Changes Analog IC design.
       
Much smaller geometries lead to "Silicon Dust".
       An example is the Tiny ADCV0831
which is a low power 8 bit ADC
.

  4) Should an Engineer change his job every 5 years?
            Does technology really change that fast?
           My resume and patent portfolio perhaps reflects such a story.


========ANALOG ART===================

1) Productivity Tools and Templates   
 
   In Electronics there always seems to be opportunity to spend time to save time.
    Some times it is far easier to just create yourself a tool in order to save a lot of work.
    A) RR Polish calculator
   B) R_C_F calculator
   C) R_C_L_F calculator
   D) Javascript Calculators

   Getting something to work often requires far more attention to detail than the help files provide.
  Working examples need to have all the required details in place just to work.
  The following "work in progress" organized working examples intended for  cut and paste
use.
   A) macspice/winspice Template web page
   B) SIMetrix          Template web page
   C) javascript        Template web page
   D) Perl              Template web page
   E) Ccode             Template web page
   F) Xcode             Template web page
   G) Web Page          Template web page
   H) Icarus Verilog    Template web page
   I) LabView           Template web page
   J) ICEDIT            Template web page
  
K) Quartz            Template web page

2) Free Spice
    Several free or semi-free versions of spice are available off the web.
    SIMetrix is a cadence/pspice like limited free version for  windows.
    Macspice is a spice-standard free version for OS X which allows scripting.
   
Winspice is the spice-standard free version for windows which almost works using the same code.
    This simple little PLL transient simulation runs off the exact same code.

3) Spice Models QA
    The design engineer using a model is the really the one responsible for the model being accurate.
    Sometimes the TC of a diode needs to be sanity checked in order to design a bandgap reference.
    Matching a model to a curve tracer is typically the first thing to do.
    The extended bipolar dynamic range of today's  BiCMOS makes a Gummel Poon Plot more critical.

4) Spice Scripting
    Designing something like an Op Amp requires testing a circuit  over  all the "corners".
    Many permutations need to be tested because a design will typically fail at a subtle "corner condition".
   
The permutations typically involves 3 temperatures, 2 supply voltages, multi-applications, and several "process corners".
    A scripting ability in Spice allow the changing of its internal simulation conditions on the fly.
    This enable  a single multi dimensional simulation to effectively test everything.
    The results
can be stored in a text file which can be further processing by a perl program.
    Simulators such as Macspice/Winspice and cadence (Ocean)  and
SIMetrix(not_free) allows scripting.
    The scripting resource can be used to  do customized testing of things like THD, capacitance, and F_tau

5) BSIM4 simplified
    The latest BSIM4 manual off the web describes about 300 model parameters.
    If one downloads the following 180nm to 22nm BSIM files off the web.
    That adds up 3300 BSIM model parameters which may or not may be critical .
    It would be convenient if all the data could be reorganized as a table.
    Acrobat Pro allows the conversion of a pdf file to the following text  file which has been slightly cleaned up.
    A simple perl program can dump all the model files into a single text file.
    Another perl program can use the previous two text files to create a table of all parameters versus process.
    The table can further be color coded to view the trends.

6) PERL and text files
    Production test data for an Analog IC is usually available as a text file.
    The previous BSIM4 simplified example shows how perl can read and reorder text data such as a data log.
    This feature can also come in handy for the 
previous Spice Automatic Testing example.
    The previous perl program that combines directories into a single text file gets a lot of use.
    Another handy program can reorganize the data within a single text file.


7) The Most Beautiful Equation in the World.
    Euler identity has been described by some as "the Most Beautiful Equation in the World".
    A FFT is really just  mapping analog signal to
Euler identity.
   
This can be better seen when the results of a FFT is  plotted in 3D.
    A javascript calculator as been developed which can also do the 3D plotting.  
   

  8) Transient Noise Simulations
    Spice programs like SIMetrix allow noise to be simulated in transient analysis.
    For spice programs like Macspice/Winspice,  a RandomPWL javascript can created the data.
    SPICE can read the PWL file and simulate and  plot  both transient and spectrum results.
    Using a Noise Transient Analysis, it is possible to  see how two noise sources add together.

9) THD Simulation using Sprectrum Analysis
     Simulating  THD  in transient  analysis shows the  actual distorted waveforms.
     Selected elements of the spectrum output can be mathematically processed to get THD .
     The classical distortion over temperature of a differential input is a good place to start.

     Adjustments of area ratios for distortion cancellation for an alternative input can also be viewed.
     The distortion profile of differential input stages all track absolute temperature.

10) Extremely Easy Ways to Generate Spice Waveforms
      By making a voltage ramp that tracks time, waveforms can be generated using equations.
      Some examples are Triangle waves, Square waves, and Ramp waveforms .
      This can be extended  to making PWM waves that can also be made to be in sync .
      Equations for Amplitude Modulation and Phase modulation also work.
      But this makes it real easy to Sweep Parameters of the Input Signal over time.

11) Play with Transmission Line Reflections
      The EDN trade magazine  has written some good articles about Time-domain reflectometry.
      Modeling transmission lines as LC subcircuits may give some vision as to what is happening .
      The various impedance mismatches can be all simulated.
      The results are all the same but all internal node voltages and currents are visible.
      The cable speed appears to simply track the time constants of resonance elements.
      Identifying and tweeking out cable discontinuities can also be played with.
     
12) Watch Noise Cancelation Work Inside an Op Amp.
      In negative feedback, an amplifier will try to cancel out all internal noise sources.
      A Noise Transient Analysis applied to an Amplifier can show everything working .
      Modeling an accurate Audio frequency Noise waveform can be very useful .
      Transistor subcircuits can then be modeled to have their noise properly track bias current.
      Observing how current noise can be modeled as input noise voltage is a good sanity check.
      N
oise operating in an Operational Transconductance Amplifier can also be observed.

13) Simulate a Pinch Resistor.
      A subcircuit can be made to follow the equations of a pinch resistor.

14) The Balanced Low Voltage BandGap.
      Need an accurate low voltage bandgap that works down to 900mV over temperature?
      The age old design technique of  balancing out errors still works .
      But balancing is only as good as it is possible to know all the errors.

15) State Variable Filters Map Equations to Circuit Components.
      Relating  the equations to the simple term of Q is a good starting point.
      The Q
terms in the equation  maps to feedback in State Variable Filters.
      The frequency terms map independently to the integrator terms.
      The equation works on resistor ratios and not absolute values.
     
Operational Transconductance Amplifier can replace the integrators
      This allows  voltage to control the frequency of a
State Variable Filter.
      It also allows complete IC integration of analog audio
frequency filters.
      The mapping comes in handy making Butterworth and Bessel filters

16) FFT Your Company's Stock Using Spice
      It is always nice to add REAL Input Signal to a Spice Simulation.
      It only requires a spreadsheet and a text editor to input any data.
      Software is being written to  convert computers into oscilloscopes.
      The line-in port can be used to digitize
Audio frequency waveforms.
      And USB hardware is being developed to digitize higher frequencies.

17) Make Some Pretty Waveforms.
      Generating Lissajous waveforms involves using the X/Y features of spice.
      Another
X/Y oscilliscope application is for BH curves.

18) Measure Stray Capacitance Within Spice.
      The scripting features in Spice can be used to measure and print out capacitance.
      This feature extends to measuring all the strays capacitances within a MOS device.
      The feature further extends into making a CV plot of gate capacitance.

19) Investigate f_tau Parameters using Spice scripting.
    
Page 72 of the Gummel-Poon Toolkit describes the f-tau situation.
      Observes the effects of changing TF or CJE or IKF or ITF or VTF or XTF.

20) Voltage Controlled Filters
    
State Variable filters can vary their frequency if made using gm_C stages.
      The Low Phase distortion of a Bessel filter will hold over all VCF frequencies.
      The flat pass band response for a Butterworth will hold as well.
      The Phase distortion of a Butterworth does change with VCF frequency.


21) Group Delay on Phase Distortion.
     The Bessel filter shows why good group delay means low phase distortion.
     The Butterworth filter shows the source of phase distortion.   

22) New Thermal Concerns.
     Silicon Oxide has one tenth the thermal conductivity of silicon.
     Oxide Isolation thermally isolates transistors.
     This simulation investigates real lab measured thermal self heating
.

23) Simple Logic Functions in Spice.
     Sometimes simple logic functions can be defined with a single spice line.
      A folded ADC method can be used to do an ADC function.
      Easy ways if  decoder  or flipflop functions are needed.

24) Interesting Effects of Distortion in Filters
      Distortion with feedback allows filter operation under multiple states
      Chaos type plots can show these effects in active filters.
      Distortion also can generate a "hang on" and "snap back" effect

25) Translating Between FM and PM
      Frequency Modulation in Spice is really Phase Modulation
      And  Phase Modulation is really Double Frequency Modulation.


     

Don Sauer... DSauerSanJose@Aol.com