This study presents the development and analysis of innovative magnetosensitive frequency microsensors based on double-collector transistor structures, intended for use in biomedical monitoring systems. The research introduces mathematical models of microelectronic magnetic field frequency transducers that incorporate the influence of magnetic fields on nonlinear equivalent circuit elements. Analytical expressions for conversion functions and sensitivity equations have been derived to enable optimised engineering calculations and sensor design. These models use various transistor configurations, such as double-gate field-effect transistors and bipolar transistors with active inductive elements. This achieves enhanced sensitivity in the range of weak magnetic fields that are typical of biological processes. Experimental validation confirms that the proposed designs demonstrate high sensitivity ranging from 60 Hz/mT to 7.2 kHz/mT in the magnetic induction range of 0–60 mT, with close agreement between theoretical and experimental results (±5%). These findings lay the groundwork for the development of cost-effective, highly sensitive microsensors for use in medical diagnostics, functional monitoring and neurophysiological applications.