I'm familiar with the term "gain" used in sound and music, but I'm having difficulty finding the definition in electronics. I'm seeing the term low gain and high gain being used in the description of the Panasonic Grid-Eye infrared sensor. What exactly is gain a measure of in electronics?
Electronic – “gain” a measurement of in electronics
gainterminology
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Most likely a common-mode voltage violation. See Figure 15 of the datasheet. Unfortunately it does not give you the limits for a single power supply, but shows you that common-mode and output voltage limits go hand in hand.
Actions that may solve your problem:
- Use dual power supply.
- Lift inputs above ground.
- Use a lower gain setting.
EDIT:
As pointed out by Dave Tweed, the datasheet does have information on common-mode and output voltage ranges for single supply. See Figure 13 on page 10 of the datasheet (your case is the blue triangular area). Your common-mode input is practically ground, so as soon as your output exceeds about 0.7 V, the limit is exceeded, and your device will not behave as specified. This will happen even if you change Vref to 2.5 V: the output limit will be 3.2 V for a common-mode input voltage of ground to become invalid.
Simple use case: you want an output higher than the internal VREF (2.048V) but don't want to add to your parts count with an external reference.
The less obvious case is what the datasheet calls "multiplier mode". In this case you keep the digital signal fixed and feed an analogue signal into VREF. That gives you a programmable gain amplifier, and the 2*VREF mode lets you have a gain between 0 and 2. That could be useful for analogue control loops or sensor biasing.
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Best Answer
Gain is just the ratio of two quantities. When talking about circuits, it's almost always the ratio of some measurement of the output of a circuit or component to its input.
As Olin said, the most common case is the voltage gain. That is, the ratio between the voltage amplitude of the output signal to the input signal.
Another common specification is power gain, the ratio of the output power to the input power.
But some circuits are best characterized by a current gain. Some (transimpedance amplifiers) are best characterized by a transimpedance gain --- the ratio between the output voltage and the input current.
Another common usage of the term gain is in antennas, where the gain of an antenna is "the ratio of the power produced by the antenna from a far-field source on the antenna's beam axis to the power produced by a hypothetical lossless isotropic antenna, which is equally sensitive to signals from all directions." (per Wikipedia)