ABSTRACT
When you read this diagram, note where wires are connected (‘dot’, see p. 212) and where wires are not connected (no ‘dot’).
The inverting input (–) is connected to the 0 V supply line, so the inverting input is at 0 V. The non-inverting input (+) is connected to a thermistor voltage divider. If the input from the divider is 0 V or less, the output is 0 V. If the input is a fraction of a millivolt more than 0 V, the output swings very rapidly to + 6V. The output changes from 0 V to +6 V when R2 precisely reaches the set temperature. In this circuit the output changes at about 25°C. Instead of connecting the (–) input to the 0 V line we can connect it to a two-resistor voltage divider that produces a different voltage. The output then changes at a different set temperature.
