Abstract: In this presentation, we will introduce a new type of photoacoustic (PA) and ultrasonic (US) signal processing circuit developed based on variable gain amplifiers. Most of existing PA and US microscopy systems works based on a single amplifier, whose gain is commonly applied to the two imaging modes at a fixed value and thus any of PA and US signals might be saturated because of the fixed dynamic range of an employed DAQ board. In this situation, our new data acquisition concept would allow more reliable signal acquisition process without any signal loss even under a fixed dynamic range of an employed DAQ board.