A high-efficiency amplifier for photodiode is often indispensable. If one takes into account the current delivered by the photodiode is very small, to amplify the signal it receives is very useful.
Although you can use a large number of different operational amplifiers to perform this amplification was used in this case a LM308, because it has a great profit, is more immune to noise than other operational and its frequency response is better (must be taken into account that the gain of an op amp decreases with increasing frequency).
This circuit is designed to receive pulses of light. If we want this amplifier is used as light detector is to remove the capacitor C1 and the photodiode must be connected directly to the noninverting input (negative symbol-) operational amplifier (leg 2).
This circuit is very sensitive and works well as a receiver of light signals.
The amplifier is configured as an inverting amplifier. This means that the waveform of the output is opposite to the entrance (Deprecated 180 °). The amplifier gain can be adjusted with the potentiometer R2.
Another way to look at this circuit is as current converter (photodiode current) to voltage (output of operational amplifier). The output voltage is the product of the photodiode current by the resistance R1.
The capacitor C2 is used in the LM308 to improve its frequency response.
This circuit can also work with the operational amplifier 741C (cheaper), but the gain and frequency response is lower. In this case the capacitor C2 is not necessary
voltage Power may be between 6 and 15 volts.
Mario Dominguez Zambrano
EES Section: 02
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