TL084H: In/Out limitation

Hideki Hayashi1

Part Number: TL084H
Other Parts Discussed in Thread: TLV9001, TLV9051

Hi team,

When customer try the below non-inverting circuit, customer see non-linear in V_IN<0.3V. Vcc=5V, Vee=GND

If I understand correctly, Vcm should be 1.5V < Vcm < 5V from datasheet. Also Vcm = V_IN. I'm not sure why there is linear in <1.5V.

Also output voltage swing limitation is also violated since its head room exists.

What is the solution for this case? lets change opamp to rail-to-rail or Vee should be negative supplied, right?

Best regards,

Hayashi

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 284830 points

Yes. I'd guess that a rail-to-rail opamp like the TLV9051/TLV9001 would be simpler and cheaper than generating a negative supply.

0 Gerasimos Madalvanos over 1 year ago in reply to Clemens Ladisch

TI__Mastermind 29076 points

Hello Hayashi,

Either solution can help in this circuit. How close to 0V do you need the output to go. If you need the output to be 0, I would supply a negative voltage on the VEE pin.

If 5 to 10mV from the rail is ok, it is easier to switch to a TLV9001/TLV9051 device.

Best,
Jerry

0 Hideki Hayashi1 over 1 year ago in reply to Gerasimos Madalvanos

TI__Expert 7600 points

Hi Jerry, Clemens,

Thanks for the solution. But I don't understand theoritically still.

If I understand correctly, Vcm should be 1.5V < Vcm < 5V from datasheet. Also Vcm = V_IN. Why is there linear in <1.5V.

Regards,

Hayashi

0 Clemens Ladisch over 1 year ago in reply to Hideki Hayashi1

Guru 284830 points

That 1.5 V value is the worst-case specification, so the typical behaviour will be better. Voltages above 1.5 V are guaranteed to be linear in all circumstances; there is no guarantee what happens below 1.5 V.

0 Gerasimos Madalvanos over 1 year ago in reply to Clemens Ladisch

TI__Mastermind 29076 points

Hayashi,

Over process and temperature variations, the non-linear behavior will start at different voltages. For robust performance, you should keep the input signal more than 1.5V above your negative rail.

Best,
Jerry

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TL084H: In/Out limitation