100 MHz Photodiode Amplifier
High bandwidth and high slew-rate current feedback amplifiers are good choices for photodiode amplifiers. An example using the Analog Devices
op-amp is shown below. The circuit is a standard voltage amplifier circuit with a gain of 20 and combined bandwidth (photodiode + amplifier) of ~ 100MHz. The circuit is
equivalent in gain to a transimpedance amplifier with Rf=1kΩ. The photodiode
was biased at -30V with a capacitance of 2.3pF. With Rp=51ohm and with 2.5pF stray capacitance, the pole at the NI input is over 500MHz. The pole in the feedback network is
also higher than 500MHz with a stray capacitance of ~ 0.3pF. Therefore these poles don't limit the frequency response.
The Vishay BPV10 Si pin photodiode has a bandwidth of 250MHz when biased at reverse voltages higher than -15V.
The scope trace below shows the optical impulse response of the photodiode amplifier circuit. The source was a 30ns wide infrared LED pulse.