TINA/Spice/TL084: Transient Simulation with TL084

dtluigi

Part Number: TL084
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

Hi, I would ask to you if is it possible to verify that the TINA model of the TL084 misses the input capacitance of its input pins; I have verified with a prototype, that the transient simulation is missing something like 20pF for each input pin.

Could you please verify?

Best Regards

Luigi

over 6 years ago

0 Paul Goedeke over 6 years ago

TI__Mastermind 30600 points

Hi Luigi,

This is an old model! It does not appear that the input capacitance are modeled. We test this by using circuits like the ones I've attached. They show only 1.3pF of common mode capacitance and no differential capacitance.

TL084 Ccm Test.TSC

TL084 Cdiff Test.TSC

I would also encourage you to look at a series of articles written by my colleague Ian Williams on testing SPICE models:

https://www.edn.com/design/analog/4460430/The-complete-simulation-test-bench-for-op-amps--Part-1--Output-impedance

https://e2e.ti.com/blogs_/b/analogwire/archive/2017/07/27/trust-but-verify-spice-model-accuracy-part-1-common-mode-rejection-ratio-cmrr

Best,

Paul

0 kai klaas69 over 6 years ago

Guru 140200 points

Hi Luigi,

when using an older spice model, like the TL084, in a simulation, I always add 10...20pF input capacitances by hand...

Kai

0 Paul Goedeke over 6 years ago in reply to kai klaas69

TI__Mastermind 30600 points

Hi Luigi,

If this has answered your question, I would appreciate if you would click the "resolved" button. I'll close the thread for now, please start a new thread or post back if you have further questions.

-Paul

0 dtluigi over 6 years ago in reply to Paul Goedeke

Intellectual 595 points

Thank you all for confirming my doubts.

Amplifiers

Amplifiers forum

TINA/Spice/TL084: Transient Simulation with TL084