The MMBF4391LT1G from onsemi is a Junction Field Effect Transistor (JFET) with Drain Saturation Current 50 to 150 mA, Gate Source Voltage 30 V, Drain Source Resistance 30 Ohm, Gate Current 50 mA, Gate Reverse Current 1.0 nA. Tags: Surface Mount. More details for MMBF4391LT1G can be seen below.