Analysis of a proposed amplifier using the electro-optic junction modulator combined with an efficient photodetector shows that gain can be expected at microwave frequencies. The power gain-band product is found to increase linearly with light source power. Calculated gain-band products , for a light power of one watt at the modulator input, a modulator length of one cm and a width of 10 microns are: for a GaAs modulator-2.6 GHz and for a GaP modulator-710 MHz. A traveling wave design shows gain proportional to the number of segments. For the same conditions as above, and using one thousand segments each 10 microns long, calculated gain-frequency products are: GaAs-820 GHz and GaP-130 GHz. An elementary noise calculation for the traveling wave design indicates that the amplifier is potentially capable of low noise operation.