TLE2064BM Output Current Capability

Hello Cabalauf,

Actually, the +/-80 mA is per each amplifier in the TLE2064BM. In reality, for most TLE2064BM devices the output current will be self-limited to something less for each output. Data sheet Figures 10 and 11 show the MAXIMUM POSITIVE and NEGATIVE PEAK OUTPUT VOLTAGE vs OUTPUT CURRENT, respectively. The typical maximum positive current looks to be about -60 mA (the minus sign means sourcing current), while the maximum negative current is about -35 mA (sinking current). These currents are typical maximums at 25C. They might be more, or less, at lower or higher temperatures, for different conditions and for different devices. 

The TLE2064BM open-loop gain (AVD) is specified with load resistances of 10 k and 600 Ohms with +/-15 V supplies, and down to a 100 Ohm load with +/-5 V supplies. This gives you some idea of what kind of output current levels the amplifier is intended to operate at. The output swing for the AVD parameter is specified as +/-8 V for +/-15 V supplies, the peak current equates to 13.3 mA for a 600 Ohm load condition. For the +/-5 V supplies, AVD specifies a swing of +/-2 V. Using the 100 Ohm load the peak load current is 20 mA.

These are reasonable high-end current levels for this amplifier. For best linear operation you would not operate the op amp its maximum output current levels such as 60, or 80 mA. Doing so results in increased distortion and limits the output swing to a lower levels. And there are the increased power dissipation concerns.

Regards, Thomas

PA - Linear Applications Engineering

Thank you for the reply Thomas. I guess I am still a little confused at how TI specifies this particular parameter (Iout) in there opamp datasheets. I have reviewed the curves you refer to as well as the rest of the datasheet pretty thoroughly.
For example, I can easily set up all four amplifiers in the device to have an output voltage of 10V each driving a 400 ohm resistive load referenced to ground. The opamp would be sourcing ~25mA a piece. Since all four amplifiers share Vcc+, the total current through Vcc+ in this configuration would be ~100mA seemingly violating the absolute maximum ratings of the device stating total current into Vcc+ is 80mA. Am I not interpreting this absolute maximum rating correctly? If not, it is very misleading and there is no clear indication that it applies to each amplifier individually.
I am trying to understand how the specification works not poke at a particular application. Thanks again for any further assistance.

Hi Thomas,

I'm glad my question was clear and you see what I was referring to. The output current capbility specified in the absolute maxmum secton seemed different and so wanted to clarify. To answer your follow up question, yes I do want to find an alternative to the TLE2064 as we would like to move away from the military specified part and find and extended industrial alterantative. -40 to +125C is imperative for the alternative and preferably quad package. Precision is not imperative, but at least 30-40mA of output drive per opamp is a must.

I was looking at the OPA4192, which seems like a much cheaper sufficient alternative. I wish TI was more explicit about the output drive capability of the opamps like some of the other manufacturers. It seems the OPA4192 has a short circuit current at ambient near 65mA but there is a note saying that is for one opamp per package. It is still unclear if I will be dissipating excessive power if all 4 amplifiers were sinking/sourcing 30mA apeice.

If you have any comments that would be appreciated or any other options. There seems to be quite a few options in the -40 to +125C range, narrowing one down can be difficult sometimes.

P.S. I also need a replacement option for the LM139 but I can take that up in another topic if I can't find one. Looks like the LM2901 might be a good alternative.

Thanks!

Hello Cabalauf,

The issue with a quad operational amplifier driving 30 mA from each output will be how much power the device must dissipate without exceeding the maximum junction temperature, Tj. For most amplifiers the maximum Tj is 150 C. Standard op amp package types that don't have integrated provisions to help with heat removal may not be able to dissipate much power before Tj rises to, or beyond, 150 C. The OPA4192 is in this class because even though each of the four outputs can deliver 30 mA, its surface-mount packaging (SOIC) would result in high power dissipation conditions. This is due to the thermal resistance of these small packages. Some op amps are offered in surface-mount PowerPad packages that have lowers thermal resistances compared to ones that don't. However, none of the quad, high-voltage (+-18 V) op amps come in that type of package.

Actually, the OPA4192 data sheet has a pretty good explanation about power dissipation and Tj in the Thermal Protection section 8.3.4. It provides an example of one of the OPA4192 amplifiers supplying 30 mA to a load, but with an ambient temperature of 65 C. In that example, the maximum Tj is exceeded and the OPA4192 goes into thermal shutdown, a self-protection mode.

Your application does indicate that it requires an op amp is designed for power delivery and dissipation. TI has power operational amplifiers that can easily handle a total current well in excess of 120 mA, but they are not available in a standard 14-pin SOIC and they are not dual, or quad, amplifiers. If you would like to explore such options I can help.

Regards, Thomas

PA - Linear Applications Engineering

Thanks again for the assistance. Power dissipation was my main concern going to a different part. IF you could provide options that would be very appreciated.
1) Assuming ambient temp, is there a quad pack that can safely deliver ~15mA (cut my requirement in half) in a standard surface mount package? I definitely need to review the power dissipation calculations to determine Tj, it has been a while.
2) Assuming I need the higher current capability and better power dissipation what other options are you thinking? Sounds like they are single opamp packages. I will need to evaluate space constraints. Might have to stick the TLE2064 in the long run, but I can certainly evaluate what else is out there.
Thanks!

Hi Thomas,
I never heard back regarding some higher current output op-amps you mentioned. Before heading down a single op-amp solution path, what is the highest output current op-amp still available in a quad package?
I did review the power calculations provided in 8.3.4 as you mentioned but I think that can be misleading although very importan. In the example given they are powering the device single-ended which leads to a larger drop and increased power dissipation in the device. If you were to power the device in a more standard +/-15 V application and used the same exact setup the drop is lower leading to dissipated power of 0.36W instead of 0.81W and at 65C that makes the final expected junction temperature only 106.7C, well under the 150C maximum. Granted you couldn't drive all four opamps in this manner but it is not the best example.

Hello Cabalauf,

We had a small crew here during the Christmas and New Years weeks; yet, the E2E forum didn't slow much. That is why some inquiries are just now being resumed, or addressed.

A point to keep in mind is that most of the operational amplifiers - unless they are specified as a power op amp - weren't necessarily designed to drive high output current. And that is despite having moderately high output short-circuit current capability. The package thermal limitations some into play. Their data sheet Electrical Characteristics table usually lists common load conditions such as 2 k, or 10 k ohms for the open-loop gain (Aol) and voltage output swing (Vo) parameters. The OPA4192 quad op amp has one of our highest output current capabilities and it will drive loads lower than 2 K ohms, but again is intended for use with higher resistance loads. We do have a brand new dual op amp, the OPA1622, and it can sink and source 100 mA, but it isn't a quad.

Also, take a look at the OPA4172. It is a quad with fairly high output current capability:

www.ti.com/.../opa4172.pdf

You point is correct about the power dissipation and junction temperature differences when the an op amp is powered by a +30 V supply, and a +/-15 V supply. I suspect the creator of the OPA4192 op amp data sheet was attempting to illustrate the worst-case condition.

Regards, Thomas

PA - Linear Applications Engineering