Transimpedance gain modelling of optical receivers employing a pin photodiode and HBT distributed amplifier combination

In this paper we discuss how the general small-signal gain formulation reported in our earlier publication may be applied in order to arrive at an analytical expression for the transimpedance gain of arbitrarily terminated HBT distributed amplifier (DA) based optical receivers. This expression includes all of the major intrinsic and parasitic elements associated with HBTs and also incorporates the primary elements of p-i-n photodiodes. The accuracy of the transimpedance gain expression is assessed by comparison with results from simulations. Graphical results based on the derived expression are presented to show how the various HBT, distributed amplifier and photodiode parameters affect the transimpedance gain performance of optical receivers. The trends shown in these graphs are discussed in relation to the general circuit properties of the combined HBT DA and p-i-n photodiode system, with a view to providing a basic insight into the design of such receivers