In photoacoustic microscopy (PAM), detection sensitivity is an important factor for determining imaging quality and depth, which can affect photoacoustic imaging applications in biomedical engineering. To improve the detection sensitivity and signal-to-noise ratio (SNR), a miniature amplifier was integrated close to an ultrasound transducer for front-end signal amplification and output impedance matching. An optical resolution PAM was developed based on the fabricated prototype transducer to perform 3D imaging of phantoms and small vessels of the mouse ear. Experimental results show that the SNR is improved by over 10 dB. The proposed PAM has the potential to be used for monitoring and quantitatively analyzing weak physiological changes.