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4.4 Current to Voltage

4.4.1 Motivation

Some sensors output a current rather than a voltage. The most common sensor of this type is the photodiode which has a current output proportional to the amount of light shining on it. The purpose of the signal conditioning circuitry is to convert the current output of the sensor to a voltage.

4.4.2 Circuits

In converting a current to a voltage, one usually uses an inverting amplifier configuration, since a non-inverting amplifier draws very little current. Figure 31 shows a current amplifier connected to a photodiode. Notice that the circuit is identical to the non- inverting amplifier with the input resistor removed. As the light increases, the current output of the photdiode increases, increasing tex2html_wrap_inline1972 proportionally: tex2html_wrap_inline1974


Figure 31: Photocell Connected to a Current Amplifier

Tim Stilson
Thu Oct 17 16:32:33 PDT 1996