| 摘要 |
To effect reliable start-up of electronic systems in which a comparator compares a measured value with a reference, particularly in which a comparator senses current flow through a temperature sensitive resistor exposed to airflow to maintain the resistance value of the resistor at a predetermined level, with respect to the reference, a start-up signal circuit is provided to supply a minimum signal to the comparator before the system is operative so that the comparator will initially provide an output to control the current source for the sensing resistor to heat the sensing resistor to its desired level. The minimum signal is derived, for example, from a voltage divider and connected over a diode to the comparator which, typically, is an operational amplifier, the diode being so poled that, when the signal from the sensing resistor exceeds the minimum signal, it will block, thus cutting off application of the minimum start-up signal from affecting further operation of the circuit.
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