The present invention relates to a Pulsed ultrasonic flaw detector designed to determine the location, size and character of internal defects in materials. An operational amplifier of the flaw detector includes a current generator circuit coupled to a capacitor that forms a control signal. The current generator has a controlled internal resistance and employs AC positive feedback provided by one of the amplifier stages of an operational amplifier. The output stage of the operational amplifier is coupled to the amplifier of the reflected signal receiver via an AC negative feedback circuit employed in one or several stages of this amplifier.
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