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.

  • linear frequency axis
  • loglog plot

Itärastit Stormossen/Spjutsund

Slow pace today due to both tired legs and slow greenish terrain. The controls were grouped into two groups with a slightly boring 'tunnel' run between the areas. OK until #4, but not the greatest direction towards #5, and then after wading through the swamp and green area towards #10 I decided from within the control-circle to go check that the yellow swamp on the right really is there... (#10 was probably the hardest control on this map). Good weather around +18 C.