A circuit model for a field emission triode has been proposed. The model parameters have been extracted from the fabricated silicon tip array and verified by being compared to the results simulated by circuit simulator (SPICE). The cutoff frequency can be calculated from the parametric capacitance and the transconductance values extracted from measurements. For the field emission triode, the capacitance of 3.45 fF/tip and the transconductance of 0.94 nS/tip have been measured under the emission current of 4.1 nA/tip. From these values, the cutoff frequency is predicted to be 43 kHz but the measured one came out to be 6 kHz because of the parasitic capacitance components.