Part Number:OPA857EVM-978
The first time I tested this board I was unable to get it functioning properly.
I spoke with a representative of TI yesterday regarding this issue and was advised to post here to determine if the board is defective as I suspect it is.
The evaluation board is intended to be used in conjunction with a photodiode for detecting 30 uA current pulses with a pulse width of 40 ns. The photodiode I am testing the amplifier with is a properly functioning silicon photodiode that I've independently verified with a 520 nm 40 ns laser pulse and a scope.
I've tested the board in test mode and in photodiode mode. I would like to use it in photodiode mode. My test connections are as follows according to section 5.2 Photodiode Mode and referring to Figure 5. Pulse Response Test Circuit as outlined in manual TIDUBX71 - April 2016:
TEST_SD = GND
TEST_IN = +VCC (equivalent to +VS)
Anode of photodiode connected to IN
Cathode of photodiode connected to VAPD
VAPD at ground (i.e. for photovoltaic mode)
VCC = 3.3 V (positive supply)
GROUND = 0V (negative supply)
J6 set to 20 kOhm position.
I've attached an image showing the jumper configurations on the board for photodiode mode.
I've noticed that the power supply sources 0.09 A at 3.3V which seems a bit high for the OPA. The rep seemed to think this may indicate a defective board.
Please advise on how to proceed.
Best,
Andre