Hi, I am designing a high current driver after a precision DAC (AD5781). I found the circuit from AN18: Power Gain Stages for Monolithic Amplifiers. In Figure 02, It uses a current boost design of NPN + PNP after a high current buffer LT1010, which is capable of driving 150 mA output. The overall circuit can deliver 3A RMS current at +, - 15V load.
We have an output buffer AD8675 after the 18 bit DAC AD5781, and we want to use the above circuit after the DAC for driving a high current load. We have the following questions,
1, is this circuit requires a special op-amp buffer such as LT1010? For example, in this circuit, the 33 Ohm to the VSS, VDD and 100 Ohm from the output of LT1010 to the ground provide biasing of Q1, Q2. Does this mean that Q1, Q2 are always on and there are minimal crossover distortions (high precision)?
2, Can we replace LT1010 with a more precision high current amplifier such as ADA4870 or LT1970A? If we can, what should we take care of in order to make this circuit stable?
3, Can we replace LT1056 and LT1010 altogether with a modern op-amp? for example, ADA4627-1, AD8675 or LT6018? We like the specification of LT6018, and would like to know whether LT6018 (AD8675) alone or LT6018 (AD8675) + ADA4870 can replace LT1056 + LT1010?
4, How to analysis the overall performance (noise, precision, temperature drift)? Is this power booster circuit preserves 18-bit precision?
Correct some typos
[edited by: byliu at 2:16 PM (GMT 0) on 30 Apr 2019]