Tool/software: TINA-TI or Spice Models
Hello,I am simulating a passive circuit for a high-voltage differential probe. The circuit consists of resistors, the distributed capacitance to the ground plane, the input capacitance of the load and a trimmer capacitor to tune out the distributed capacitance and the input capacitance to the load. The DC path from signal source to the load consists only of series resistors of value 125k and one load resistance of 5k . Thus, there is no gain and there are no shunting resistors of any sort. One capacitor is in parallel with each resistor, and there is a capacitor to ground at each connection between resistors.
When I run an AC analysis and select the "AC Transfer Characteristic", I select a frequency sweep from 1 Hz to 100 GHz.
To my surprise, when Tina-TI simulates the circuit, it reports a gain of -37.6 dB from 1 Hz to 1 Megahertz. However, the hand-calculated gain is actually -40.08dB because the four 125k resistors in series total of 500k, and they feed a load resistor of 5k so the result is a 5k/505k divider which has a DC gain of -40.08 dB. The capacitors play no part because they have values in the low pF range and the frequency at the lower end of the sweep is much too low.What is wrong here? I can provide you with my .tsc file if you tell me how to get it to you.Regards,Peter
Nikhil Gupta | Product Folder Modeling Manager | Online Design Tools
All TI Spice Models can be found here | All WEBENCH supported devices can be found here
In reply to Nikhil Gupta (1):
In reply to Peter Gregson:
Peter, Refer to these FAQs: e2e.ti.com/.../148.4-5-attaching-a-file
Please find the .TSC file as requested.
The 1st resistance in your circuit is marked as 125 ohms instead of 125KOhms. Once you fix that you should get expected results.
Good catch indeed! Thank you.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.