Other Parts Discussed in Thread: THS6012, TPA6120A2, OPA1602, OPA1612, OPA2210
The TPA6120A2 and THS6222 are comparable in terms of cost for in-loop composite applications. The former appears appropriate for a gain of 10, though examples are thin on the ground. The latter is clearly designed to be “high” gain capable, but due to its market segment has some quirks that I need to dig into here. The THS6222 has the significant advantage of lower quiescent current, and I’m guessing there are a lot of other improvements that TI has made since the THS6012 came out.
So, regarding the THS6222:
1) Other than the mild bandwidth limiting associated with Low Bias mode, what are the other results? There is a reference to increased distortion, but no data to shed light on the topic. If you set up the amp for Low Bias and add resistance to ground at the Iadj point, you can significantly decrease Iq, but what happens as you dial from 0R to ~6K? Are there further bandwidth and distortion tradeoffs? To what degree?
2) Clearly, the amps must be used differentially due to the T-bias network. But what else defines this part’s differential-only requirement? The data sheet does not clarify. If the amps are given gain via the expected Rg/Rf network, a single-ended input should balance to a degree, but not fully (within 6dB IIRC). Does this part exhibit that typical behavior? If the amps receive a differential signal that is somewhat imbalanced (again within 6dB) is there a specific performance degradation or limitation? What happens?
3) Pardon my inexperience with IMD in high speed environments: Does the egregious ramp in IMD below 1MHz matter if the amps are used in-loop? What else does the IMD graph indicate about this part at audio frequencies? Are we simply looking at the results of two tones around 1MHz and if we saw the results of two tones conventionally used within the audio band we would have a completely different graph? Can you make that graph, if deemed necessary?
Dual 15 or 16V supplies, by the way. Lead op amp is anything in the OPA1612, OPA1602, OPA2210 genre. Output of 16dBu to 28dBu, differential, depending on application. The part might not quite hit that top mark but comes close enough IIRC.
