In this paper, the design of a monolithically integrated electro-optical transmitter is studied. The circuit was realized in an electro-photonic 250-nm technology which integrates a silicon photonics Mach-Zehnder modulator (MZM) and an electrical Bi-CMOS driver on the same chip. The circuit reaches on-off keying data rates up to 37 Gb/s, thus being, to the best of the authors' knowledge, the fastest monolithically integrated electro-optical transmitter in the literature (in terms of symbol rate). We show that by employing a high-swing, open-collector electrical driver, a compact MZM assembly with short-length phase shifters (2 mm) can be realized, while still reaching a high extinction ratio (ER) of 7.6 dB (at 35 Gb/s). The open-collector design approach allowed to increase the data rate while reducing the DC power consumption. In this work, we prove that one of the main drawbacks of MZM-based transmitters, namely their large chip footprint, can be overcome without sacrificing the speed, ER or the power consumption of the transmitter.