VCA822: VCA822

Betül Günçaldı

Part Number: VCA822

I want to design programmable gain block with VCA822. The IC has 100V/V gain range but at simulation, the recommended resistor values for 100V/V (Rf = 845 ohm, Rg = 16.9 ohm) do not provide 100V/V at VG = 1V. The result has big offset. However recommended resistor values for 10V/V ((Rf = 1000 ohm, Rg = 200 ohm) provide 10V/V at VG = 1V. Why is there so much difference these gain configurations?

9 months ago

0 Betül Günçaldı 9 months ago

Prodigy 30 points

Also, if I use 1000k and 20ohm resistor values for 100V/V, will VCA822 work? Do I have to use these resistor values recommended at datasheet (845 ohm, 16.9ohm)? Even the recommended values do not work properly in the simulation.

0 Betül Günçaldı 9 months ago

Prodigy 30 points

In this configuration VCA822 does not work properly. But this configuration is appropriate for differential inputs. Result :

+1 Nick Nauman 9 months ago in reply to Betül Günçaldı

TI__Expert 6050 points

Hi Betul,

It is very odd that you are seeing these simulation results. I created a simulation for the differential configuration you are looking to test and I am getting expected results. I have attached that file so you can try running the simulation with this file.

VCA822_E2E.TSC

To address your question about about resistor values: The recommended resistor values listed on the datasheet are selected to give the best distortion performance. Also, all electrical characteristics are tested using these values. The resistor values can be changed if needed but that could have an effect on the device performance.

Please let me know if you have any other questions.

Thanks,

Nick

0 Betül Günçaldı 9 months ago in reply to Nick Nauman

Prodigy 30 points

Thank you.

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VCA822: VCA822