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LM293A: Common mode input voltage understanding

Part Number: LM293A
Other Parts Discussed in Thread: LM293

Dear all：

For the LM293, the input voltage should be less than 3.5V at room temperature, and 3V over temperature. We recommend the 3V limit.——This is the specification.

The "common mode input voltage" should be less than 3V, is it consistent with our understanding that the voltage between IN- and IN+ of the comparator and the supply negative (GND) of the comparator should be less than 3V?Or is it something else?

for example：

The following is the description of the specification：

But here's how it works：

(1) IN the first stage, the voltage adjustment of U5A IN+ to GND is 4.5v, and the voltage adjustment of IN- to GND is 4V, and the output is 5V, (correct)
IN the first stage, the voltage adjustment of U5A IN+ to GND is 4.5v, and the voltage adjustment of in-gnd is 5V, and the output is 0V, (correct) which is inconsistent with the specification description

(2) voltage adjustment of U5A IN IN the first stage to GND is 4.5v, and voltage adjustment of IN+ to GND is 5V, and output is 0V, (error)
IN the first stage, the voltage adjustment of U5A IN to GND is 4.5v, and the voltage adjustment of IN+ to GND is 0V, and the output is 0V, (correct) which is consistent with the description IN the specification

So am I wrong about the definition of the common mode input voltage?

Thank you！

• Hi Timsen,

it's very simple: With a supply voltage of 5V the input voltages of LM293 should stay within the range of 0V and 3V over temperature. Exceeding these limits will result in a degradattion of performance, like input offset voltage, response time, etc.

Kai