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Alternative to OPA140 to drive higher capacitive load

Steffen
Prodigy 30 points
Other Parts Discussed in Thread: OPA140, OPA4140

Hello,

I am looking for an alternative to the OPA140 which is capable of driving a higher capacitive load? 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 prefer to use an op amp without differential input clamp diodes.
The op amp is configured as unity buffer. The load resistance is 10kOhm and the load capacity is about 1.5nF. 

The supply voltage is +14V and the negative supply is -12V. Furthermore, the application requires a slew rate >= 5V/µs.

The data sheet of the OPA140 recommends using a small resistor in series with the output for heavier capacitive loads. According to the accuracy requirement of my application, I cannot use a series resistor above 10Ohm.

Can you recommend me an alternative op amp fulfilling the above mentioned requirements? Or would you recommend using the four amplifiers of an OPA4140 in parallel?

Regards,

Steffen 

  • 0
    TI__Guru 64060 points

    Steffen,

    We have some robust low voltage op amps capable of driving uF's of capacitive load (e.g. OPAx350) but there are very few high voltage (Vs>20V) op amps available with no differential input clamps, capable of directly driving 1500pF load in a follower configuration - OPA140, you have chosen, is one of the best in this respect.

    Based on the Small-signal Overshoot vs Capacitive Load graph below, I would expect that placing 10ohm output resistor in series with 1.5nF load might just be enough to assure stable operation, even though with some output settling time ringing, as shown below (~40% overshoot) - however, this needs to be verified by prototyping the circuit.