TINA/Spice/LM358: About simulation result

Charles Jeon

Expert 2975 points

Part Number: LM358
Other Parts Discussed in Thread: TINA-TI, , LMH6644,

Tool/software: TINA-TI or Spice Models

Hi team

I ran the LM358 simulation via TINA as an attach file.

Final output voltage is less than 100mV.

In the actual circuit, about 1.1V is output.

I wonder why the difference occurs.

Please check and reply.LMH6644.TSC

over 7 years ago

0 Herman Theodorus over 7 years ago

TI__Genius 9775 points

Hi Charles,

I'll move this post to product specific group that can assist you further.

Herman

0 Paul Goedeke over 7 years ago in reply to Herman Theodorus

TI__Mastermind 30600 points

Hi Charles,

Can you help me understand what the circuit application is? I tried replacing the LM358 with an ideal amplifier in TINA and the output goes to -8V, which tells me that the op-amp model is probably hitting its negative rail.

If you can provide some clarity on the desired operation and the input signal magnitude/frequency, that would be helpful.

Thanks,
Paul

0 Charles Jeon over 7 years ago in reply to Paul Goedeke

Expert 2975 points

HI Paul

It is a circuit that adjusts the output level of the two-stage amplifier by changing the duty of VG1.
The output voltage is only controlled by Positive.

Thank you

0 Ron Michallick over 7 years ago in reply to Charles Jeon

TI__Guru**** 165376 points

Charles,

I suggest using the newer LM358 model available on the product page for LM358. The one built into TI-Tina is older. This model is closer and shows an output at 645 mV which seems right to me. See figure 9 in LM358 data sheet. LM358 can only output 100 mV when sinking current is only a few micro amps.

Switching our new LM358LV would solve this issue. Otherwise remove R17 and increase R7 to reduce the LM358 sinking current needed.