A digital amplitude quantizer is disclosed having sequential stages each for measuring a selected portion of the overall range of the level of power of applied RF signals. Each of the sequential stages comprises a serial arrangement of a directional coupler, a detector, an amplifier and an analog-to-digital converter. The directional coupler of each stage is activated when it receives a predetermined level of power of the applied RF signals. The sequential stages further comprise a series arrangement of PROMs and latches that are shared by adjacent stages. In operation, the RF amplifier in the uppermost or last stage is commonly driven into its limiting condition by appropriate RF signals. When the uppermost stage is nearly into its limiting operation, the directional coupler in the preceding stage receives a sufficient level of power of the RF signals and continues to do so until its related RF amplifier is also driven into limitation. When this preceding stage is nearly into its limiting operation, the next lower stage is activated and begins its operation. The sequential or chain-like interrelationship continues until all the stages in the quantizer participate in the measurement of the overall range of power of the applied RF signals. Also, in operation, shared PROMs generate a digital quantity and control their latches so that a composite digital representation is provided and indicates the power level of the applied RF signals.