Abstract: A surgical instrument, has an end effector that includes an ultrasonic blade, and a clamp arm that moves relative to the ultrasonic blade from an opened position toward an intermediate position and a closed position. The clamp arm is offset from the ultrasonic blade to define a predetermined gap in the intermediate position between the opened position and the closed position. A clamp arm actuator connects to the clamp arm and moves from an opened configuration to a closed configuration to direct the clamp arm from the opened position toward the intermediate position and the closed position. A spacer connects with the clamp arm to inhibit movement of the clamp arm from the intermediate position toward the closed position for maintaining the predetermined gap between the clamp arm and the ultrasonic blade.

Abstract: A powered transducer preamplifier includes a preamplifier circuit that DC couples the preamplifier input with the preamplifier output. A biasing circuit is coupled to the preamplifier input to apply a bias voltage to power the transducer, and a DC level shifting circuit is DC coupled to the signal path of the preamplifier circuit between the input and the output to compensate for this bias voltage. The DC level shifting circuit avoids the use of reactive components, and thereby reduces phase distortion. A variety of DC level shifting circuits can be used, including a bridge circuit having four matched resistors and an inverter DC coupled between the nodes of the bridge.