The triode is similar in operation to the n-channel JFET; it is normally on, and exhibits progressively lower and lower plate current as the grid/gate is pulled increasingly negative relative to the source/cathode. Cutoff voltage is equivalent to the JFET's pinch-off voltage (Vp) or VGS(off); i.e., the voltage point at which current stops flowing entirely. This similarity is limited, however. The triode's anode current is highly dependent on anode voltage as well as grid voltage, causing it to appear as a voltage source in circuit. The JFET's drain current is virtually unaffected by drain voltage, thus it appears as a constant-current device, similar in action to a tetrode or pentode tube. Both the JFET and tetrode/pentode valves offer much higher voltage gains than the triode.