Photodiode Preamplifier using GainAmp/Open-Loop Op Amps
Created: Apr 05, 2016
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A photodiode is capable of short distance wireless transmission with the help of an amplifier circuit. The design features open-loop, unity-gain-stable op amps that are built into an integrated circuit and makes it more compact and low cost. The input bias current is 200pA max and stable with capacitive loads up to 100pF with no isolation resistor.
The amplifier circuit of the photodiode consist of some discrete components. A 0.1uF bypass capacitor is connected between power supply and ground that minimizes lead inductance and noise. The coupling capacitor is provided in the inverting port of the amplifier that rejects unwanted low-frequency signal. The resistor in the feedback path valued 1.5MΩ that determines the sensitivity of the circuit. The 100pF capacitor helps to prevent instability of the circuit.
It is suitable to IrDA applications and some handheld devices. The quad op amp IC is provided with identical circuit that is applicable in high-speed parallel optical links. It can be modified easily for specific applications and can be used for evaluation of visible and infrared light applications.