A study of the frequency response and gain of Solid-state the Impact-ionization Multiplier (SIM). The SIM generates current gain via impact ionization also known as avalanche gain. The SIM provides low noise amplification from an arbitrary current source. In the case of this study, current sources consisted of photodiodes optimized for a particular wavelength of light. The SIM is fabricated from silicon and enjoys the low noise, low carrier transit time advantages of conventional silicon impact ionization devices while amplifying current from a photodiode of a different material. This is advantageous because ideal detection and multiplication regions cannot always be grown on the same wafer. Furthermore a photodiode fitted to a SIM allows absorption and multiplication regions to be independently optimized. The SIM exhibits a current dependant input resistance. This resistance in combination with field effects from the SIM collector is the limiting factor in the frequency response of the SIM. Frequency response is improved to the extent that this floating voltage at the input can be minimized. Higher AC gains are realized in the device with the incorporation of 3-dimensional geometries. These improvements allow for improved device breakdown and reduced space-charge resistance at high input currents. Frequency response can also be improved by increasing the current flowing into the SIM, this current is most often in the form of DC current such that it can be filtered off at a the output and not interfere with the input signal.