OP AMP Block Diagram?

Question

I need a block diagram based on an op amp, where a red light comes on if the temperature rises above 20 degrees and a green light if it drops below 20C, on the output of the circuit.

Answer 1

What you are looking at, is a comparator circuit. An input from temperature sensor (voltage source) goes to the + side of the input.

A reference source goes to the - side of the input.

Depending on which one is higher, the output will swing from + max to - max. You need to have transistor in darlington configuration at the output to drive the light. (or a single transistor if you are using LED)