In this paper, two schemes of generating reference voltages using enhancement-mode MOS transistors and resistors are proposed. The first one is a voltage-mode scheme where the temperature compensation is made by summing a voltage component proportional to a threshold voltage and a voltage component proportional to a thermal voltage. In the second one, that is a current-mode scheme, the temperature compensation is made by summing a current component proportional to a threshold voltage and a current component proportional to a thermal voltage. The designed circuits have been simulated using a $0.65{mu}m$ n-well CMOS process parameters. The voltage-mode circuit has a temperature coefficient less than $48.0ppm/^{circ}C$ and a power-supply(VDD) coefficient less than 0.21%/V for a temperature range of $-30^{circ}C{sim}130^{circ}C$ and a VDD range of $3V{sim}12V$. The current-mode circuit has a temperature coefficient less than $38.2ppm/^{circ}C$ and a VDD coefficient less than 0.8%/V for $-30^{circ}C{sim}130^{circ}C;and; 4V{sim}12V$. The power consumption of the voltage-mode and current-mode circuits are $27{mu}W;and;65{mu}W$ respectively for 5V and $30^{circ}C$. Measurement results show that the voltage-mode reference circuit has a VDD coefficient less than 0.63%/V for $30^{circ}C{sim}100^{circ}C$ and has a temperature coefficient less than $490ppm/^{circ}C;for;3V{sim}6V$. The proposed reference circuits are simple and thus easy to design. The proposed current-mode reference circuit can be designed to generate a wide range of reference voltages.