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Original question:

LM2907-N: The output can not adjust when the input frequency changed.

LM2907-N: Simulation and measurement issues

romain vincenot
Prodigy 10 points
Part Number: LM2907-N

Tool/software:

Hi, 

I ran a simulation using the model from this discussion : 

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1211618/lm2907-n-frequency-to-voltage-converter-circuit

At 125Hz:

Vout in theory:

Vout=f*C*R*Vcc=125*10*10E-9*47*10E3*3.3= 193.8mV

Vout from the simulation:

Vout= 183.1mV

Vout measured:

Vout=104mV

Can you tell me why there's a significant difference between the theoretical value and the experimental one?  

Thank you in advance.

 

  • +1
    TI__Guru 61511 points

    Hi Vincenot,

    The LM2907-8 will require minimum 6Vdc in order to turn on the onboard comparator. Please try to increase your Vcc above 6Vdc and it will work better. 

    Best,

    Raymond