• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 47 subscribers
  • Views 95 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LOG200: LOG200 simulation problem

jeno.zhang
Expert 2895 points
Part Number: LOG200


Tool/software:

Hello,

The following figure shows the simulation results of LOG200 using TINA. The simulation results do not match the formulas in the manual. The customer has included the Boltzmann constant and elementary charge, and the calculated value should be around 60mV/Decade. Could you please help me check if it is a problem with the settings or if there is a problem with the customer's calculation? Thank you!

  • 0
    TI__Genius 15770 points

    Hi Jeno, 

    Could you clarify what the input current range you are trying to simulate is? And are you using the IBIAS pin as a current output? If not, this pin should be left floating. 

    Regards,
    Ashley

  • 0 in reply to Ashley Kang
    Expert 2895 points

    Hello,

    1. The excitation signal is a 1uA DC bias, peak to peak 200nA, 30KHz frequency sine signal.

    2. The IBAS pin description is shown in the following figure. Whether it is float or connected to VS+, it has no effect on the simulation results. When float, TINA will also pop up a warning.

    LOG200-sim.tsc

  • 0 in reply to jeno.zhang
    TI__Genius 15770 points

    Hi Jeno,

    How is the customer calculating and verifying the scaling factor? Scaling factor is internally set to 250mV/decade for the typical current range shown in the electrical characteristic table. 

    What is the output range that the customer is trying to achieve? The log amps are optimized for wide input current ranges but it seem the input current provide is a small range that does not span multiple decades.

    Regards,
    Ashley