In this paper, a low-voltage low-power rail-to-rail constant gm transconductance amplifier (TA) is introduced. The supply voltages are set at (± 1.5 V). The circuit depends on selecting the maximum transconductance (gm) to achieve an almost constant gm over the entire common-mode (CM) range. The circuit is then used to realize a second-order 4 MHz lowpass filter consuming 530 μW, and a fifth-order 450 kHz lowpass elliptic filter consuming 2.3 mW. Both filters can be integrated on silicon without any external connections.