Hi there,
I'm quite new to the field of operational amplifiers. I've built a simple peak detector (similar to the one shown here) using the LMC6482 for detecting the maximum value of a slow signal (rise time approx. 100 us). In the circuit, the LMC6482 has to drive a capacitive load of 10 nF and exhibits ringing (or oscillations). I've added a 150 Ohm resistor as suggested in Fig. 60 of the datasheet and that removes ringing. Fine. However, I've difficulties to fully grasp the datasheet regarding capacitive load characteristics and compensation circuits.
Figure 49 and figure 52 show "Stability vs. capacitive load" for the same configuration except gain. Figure 49 has unity gain, figure 52 has a gain of 10. Apparently this increase in gain by a factor of 10 moves the "25% overshoot" margin by a factor of 1000 (note the different labels on the vertical axis). In my circuit the gain is set to unity so rather Figure 49 applies. As such the op amp is operated in the realm of instability. Is this the correct interpretation of the graphs?
To increase the op amps capacitive load tolerance, the datasheet suggests two circuits: figure 60 is a simple resistive isolation of the capacitive load (that's the solution I used) and figure 62 shows a circuit with "improved frequency response". The results are shown as analog scope pictures: figure 61 and figure 63. I cannot observe any difference between the two pictures. Where is the "improved frequency response" reflected in figure 63 compared to figure 61?
Thanks a lot for your help.
Dan
