I want to set the gain of an opamp accurately using an potentiometer, with low thermal drift and good long-term stability. From what I've read, there are three basic ways of doing it, but none of them performs really well.
The first way is simply using a potentiometer as a variable resistor. Unfortunately, it means the uncertainty and drift of the potentiometer's end-to-end resistance is fully incorporated into the gain equation.
The second way is using the potentiometer as a real potentiometer (divider).
In this configuration, as it's only a voltage divider, only the relative position of the wiper matters, the absolute end-to-end resistance of the potentiometer is not important, thus a much higher accuracy is possible. Thus, it's recommended that a potentiometer should be always used as a potentiometer if possible.
Unfortunately, because how the potentiometer is connected here, the gain of the amplifier's adjustment is highly nonlinear, and probably unsuitable for most applications but audio.
Source: Analog SEEKrets, by Leslie Green, fair use.
It's possible to linearize the gain in Configuration 2 using two additional resistors. However, the gain is, again, depends on the absolute magnitude of the end-to-end resistance of the potentiometer, making it less useful.
Are there better ways to make use of a potentiometer, without purchasing a more expensive one with better tolerance?