Hi all, recently, I use the Keithley 2602B SMU and AFG arbiartry function generator to test the I-t curve of organic electrochemical transistor (OECT). In this measurement, the AFG was set as a gate generating voltage pulse (T=1 s, High altitude= 1 V, and Low altitude = 0), and SMU adopted as drain and source (source is the LO connected to ground) with gate is 0V. Detials are listed in FIgure1. In this way, I cannot get the a gradual rising or falling current with time as reported in many literatures. There is a periodic changed current with huge current range. (Figure 1) However, keep all settings the same, the gradualy changed I-t curve can appear (shown in Figure 2) when I use the keysight+AFG. I'm so confused if this is a wiring error on my part or something else with the instrument.