The theory and practical realization of a broadband quantum-noise generator based on an original integrated optical beam splitter in the form of a Mach-Zehnder interferometer is demonstrated. The beam splitter with a double output, made on a lithium niobate substrate, provides accurate electro-optical balancing of the homodyne quantum-noise detection circuit. The experimentally obtained excess of quantum noise over classical noise is 12 dB in the frequency band over 4 GHz, which is the best parameters of quantum-noise generators known from the literature.