Part Number:OPA857EVM
Tool/software: TI-RTOS
Hello;
I have purchased OPA857 EVM for transimpedance amplifier circuit measurement and avalanche Photodiode pulse measurement for my P.h.D thesis.
First I have connected J4 (And I limit the current but when I connect J4 its trying to draw more current each time) for +VS=3.3v to Test_in input. After I put it in the APD mode. 20K gain. 5 V through the APD Bias Voltage. When I cover the photodiode I have measured the voltage differences R6 AND R7 independently but There is no voltage change in the R8 that I can measure. and the Resistance seem like 0 ohm on that resistor. And also I can not take any voltage change across the transformer. I Have measured almost every part. I can only find 2 different things R8 seems like 0 Ohm and Reference voltage sometimes can be quite faulty when I limit the current(Because I am afraid it can burn the opamp thats why I limit it to 50ma).
My application is I will make some very fast pulses from LED and try to measure it through the EVM but I couldn't do it.
Could you please help me with it3
Thanks in advance.
Best regards.