200MHz photodetector with OPA818, FGA01FC InGaAs photodiode, and RF=4k7

Here's another one-inch-photodetector using OPA818 with a 2pF@5V InGaAs fiber-coupled photodiode FGA01FC. With a transimpedance gain of 4k7 Ohms the bandwidth is just over 200 MHz. A TIASim model predicts the dark-noise and response reasonably well with a parasitic capacitance (over RF) adjusted to ca 0.12 pF. The spectrum-analyzer settings weren't ideal for looking at the dark-noise which should go down to the thermal-noise of the 4k7 resistor (dashed line) - but here the instrument noise-floor prevents us from seeing that.

400+ MHz photodetector with OPA818

One-Inch-Photodetecor in Thorlabs 1" mount. LT3093 negative-rail voltage regulator at the top, and LT3042 positive rail voltage regulator bottom right. OPA818 op-amp bottom center, with BUF602 output-driver bottom left.

After a number of failed attempts (with HMC799, OPA859), here is a reasonably fast One Inch Photodetector using OPA818, a FDS015 photodiode, and 1.2 kOhm transimpedance. Bandwidth is above 400 MHz, with the dark-noise and frequency-response in reasonable agreement with TIASim predictions.

With the detector blocked there's quite a lot of electrical feed-through with just the spectrum-analyzer TG-output on (see blue data points, especially above 1 GHz). I tried to correct for this roughly, shown as the orange data points.