Hi, I would like to use ADA4870 as high current (~1A) driver after DAC. Can it be used with ADI's 18 bit or 20 bit DACs such as AD5781 and AD5791?
I found that ADA4870 has a low noise density but a relative high Vos and Vos temperature drift. It is of much value if it can be used in high-precision, high-current systems.
I'm looking into this and also contacting some DAC product owners to give you a good recommendation.
Thank you. We would also like to find some amplifiers that may finally generate 3A~5A rms, 7A~10A peak current with a voltage span of 30V to 60V. ADA4870 might be our first try. I find that a class AB amplifier (LM3886) or handcraft NPN + PNP (crossover noise) booster is often the recommended answer. But LM3886 has large temperature drifts and I am new to high power designs, build a new class AB amplifier using NPN + PNP is challenging. We need some high power, yet high precision solutions that worth the price of high-performance 18-bit or 20-bit DAC.
Therefore, the product such as ADA4870 or LT1210 is more suitable for our needs. Driving a high current load such as a DC motor may require multiple ADA4870, which cost 4x8.5=34$ at least per design.
We are waiting for an ADI solution to this problem. Thanks!
ADA4870 is the nearest part we could offer based on your requirements considering the output current and supply range. If you are concerned about precision, take a look at page 23 of the datasheet, you could configure a composite amplifier to do the job but still more often you need a power transistor (FET or BJT) in the output of the opamp to further boost the output current drive.
Going back to Vos, if the Vos will have the same impact on each DAC code, then technically the resolution isn’t changed. In a closed loop system, the loss in precision due to Vos can still be compensated by calibration.
Thank you. I notice that figure in the Datasheet and would like to use a combination of AD8675 (or LT6018) + ADA4870 to build this composite amplifier. I also want to maintain the precision of ADA4870 for high current drivers. How could I build a power output using ADA4870 and BJTs (with minimal crossover distortions)?
... (follow up) If I want to parallel multiple (8) ADA4870 for higher current output, should I repeat (duplicate) each block of the composite amplifier on page 23? i.e., 8 * (ADA4637-1 + ADA4870-1) or I only need 1 ADA4637-1 and 8 ADA4870-1?
8 * (ADA4637-1 + ADA4870-1)