Hi,
Oh you mean the last stage without the lower section. Ok i understand you better now.
In that case just ground the 10k resistor that normally connects to the lower section output buffer. You'll still have the 10k and 100k pairs. It may work to just ground the non inverting terminal, but i'd go with the two resistors and that way you'll be ready for the lower section once the upper section is fully tested.
BTW i should clarify something. The slew rate increase we talked about earlier does in fact increase with the two current mirrors, but there may be a drawback to using just an op amp for the output stage. I'm currently still looking into this.
If we used a pair of current mirrors on the output stage too with another buffer then we might get away with more, like a higher output voltage peak as well as a bandwidth increase.
Here are some notes that apply when usinn the LM358. Note that we are not really limited to this particular op amp, but just for example i used the specs for this op amp because we are using that model and everything scales to other op amps anyway.
Specs:
Gain bandwidth product (GBP): 1000000Hz
Slew rate: 500000 v/s
Slew rate limited max bandwidth, 1v peak output: 80kHz
Slew rate limited max bandwidth, 0.1v peak output: 800kHz
Bandwidth limit due to GBP, any output, gain of 1: 1Mhz
Bandwidth limit due to GBP, any output, gain of 10: 100kHz
We have to make sure that the slew rate limit AND the bandwidth limit are both satisfied in order to create a real workable circuit, so for example in order to see an 80kHz bandwidth we'd have to keep the max output to 1v peak and max gain of 10, and to see an 800kHz bandwidth we'd have to keep the max output to 0.1v peak and a max gain of 1.