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Alternative to OP140 with increased V_CM

Steffen
Prodigy 30 points
Other Parts Discussed in Thread: OPA140, OPA132, OPA171, LM6142, LM6211, OPA209, OPA604, THS4601, TLE2141

Hello,

I am looking for an alternative to the OPA140 with an increased Common-Mode Voltage Range? My application is similar to the one in figure 3 of http://e2e.ti.com/blogs_/b/thesignal/archive/2012/03/21/differential-input-clamps-can-they-affect-your-op-amp-circuits.aspx

Due to the high slew rates in such an application, I would prefere to use an op amp without clamp diodes in the op amp input.

My supply voltage is +-12V, and according to the data sheet of the OPA 140, the upper limit of the Common-Mode Voltage Range is (V+)–3.5. The input signal range of my application is +-10V. Therefore, I am looking for an alternative to the OPA140 with a higher Common-Voltage Range.

Further more, the application requires unity-gain stability, slew rate > =10V/µs and output current >=4mA.

Regards,

Steffen 

  • 0
    Guru 21975 points

    Steffen,

    Handling +/-10V signals on a +/-12V supply is a tight squeeze for this type of op amp. For a multiplexed input you would probably want a JFET or CMOS input.

    OPA132 is specified for 2.5V from the rail with a typical of 2V. A near miss.

    OPA171 is a CMOS device, somewhat slower, that is specified for 2V from the positive rail. Problem is that it has differential input clamps.

    Let's see if others can suggest an alternative.

    Regards, Bruce.

  • 0
    TI__Guru 50016 points

    Hello Steffen,

    The diodes prevent the reverse B-E breakdown of the input stage devices, which is typically about 7V. So devices with a supply voltage over 5V will generally have the diodes to prevent breakdown of the input stage during slewing events. Some devices with diodes add series resistors to limit the current and also allow full differential voltage range.

    But you will see the diodes prominently on low noise, precision, or high speed devices where the input series resistance will affect performance.

    You are asking for no diodes, on a fast device, at a supply voltage of 24V....so what you are asking is contradictory to all the rules! :^). This is why it is difficult to find a device that meets your requirements.

    But FET devices are generally a bit more forgiving, so they may not need the clamping diodes. But FET devices tend to be slower and may have less common mode headroom.

    So I would suggest looking at the following devices:

    LM6142/44 - Bipolar input, R-R input, 17MHz, slew enhancement, does have clamps and series R, but may slew fast enough not to see them.

    LM6211 - CMOS input, low noise, tight upper common mode limit.

    OPA209 - Bipolar input, Vcm limit is 1.5V from the rail (max, typ should be better).

    OPA604 - FET input - though common mode is tight.

    THS4601 - FET input, Fast, tight common mode

    TLE2141 - Bipolar input, slower, tight common mode limits

    Hope this helps!

    Regards,

  • 0
    TI__Intellectual 1250 points

    Hello Steffen,

    In which location of TRW are you working - I am supporting TRW Koblenz and radolfzell in Germany . Please do not hesitate to contact me under r-machinal@ti.com if

    you have further technical inquiries.

    Best Regards,

    robin