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This paper introduces the design of integrated BiCMOS current-sensing circuit and amplifier for high-performance current-mode dc-dc boost converter. By exploiting the advantage presented by the integration of both CMOS and bipolar devices within same technology, the BiCMOS circuits offers high-gain amplifier and accurately sensed inductor current. The error amplifier has BJT differential pair and current sources to obtain a fast response, while the current-sensing circuit exploits a current-mirror instead of opamplifier as a voltage follower. The test in 0.35-μm BiCMOS process shows that the transient time of the error amplifier is about 4 μs and the current-sensing circuit can operate with accuracy of 88% at the frequency of 20 kHz. The output voltage of 4.8-8 V is obtained at the input voltage of 3-5 V with the ripple ratio within 5%.