It's Just a Triangle, or What Does a Symbol Really Mean?

In the analog world, a triangle can represent an op amp, a comparator, or an instrumentation amplifier. Most op amps have open-loop gain between 100,000 and 10 million, but some of the older high speed op amps might be as low as 3000. (1) A CL = × 1 ß 1 1 + 1/A VOL × ß For an op amp, we really need negative feedback; for a comparator, we really need positive feedback; and for an in-amp, we don't need any feedback. Comparisons of Op Amps, Comparators, and Instrumentation Amplifiers Op Amp Comparator In-Amp Feedback Negative None/positive Internal Open-Loop Gain 5k to 10 million 3k to 50k Fixed 0.2 to 10k Closed-Loop Gain Usually < 10,000 Fixed 0.2 to 10k Input Caps Never Maybe Good Output Analog/linear Digital Analog/linear Important Specs V OS, GBW/PM Prop delay CMRR Programming R or C None R, SPI, jumpers Let's see how you can get into trouble … Feedback An op amp has a huge gain. [Extracted from the article]