Surgical generator for ultrasonic and electrosurgical devices

A generator to communicate a drive signal to a surgical device, the generator comprising:

• a power amplifier to receive a time-varying drive signal waveform, the drive signal waveform generated by a digital-to-analog conversion of at least a portion of a plurality of drive signal waveform samples, an output of the power amplifier for generating a drive signal, the drive signal comprising one of:
• a first drive signal to be communicated to an ultrasonic surgical device, a second drive signal to be communicated to an electrosurgical device;
• a sampling circuit to generate samples of current and voltage of the drive signal when the drive signal is communicated to the surgical device, generation of the samples synchronized with the digital-to-analog conversion of the drive signal waveform samples such that, for each digital-to-analog conversion of a drive signal waveform sample, the sampling circuit generates a corresponding set of current and voltage samples;
• and
• at least one programmable device programmed to, for each drive signal waveform sample and corresponding set of current and voltage samples:
• store the current and voltage samples in a memory of the at least one programmable device to associate the stored samples with the drive signal waveform sample;
• when the drive signal comprises the first drive signal:
• determine a motional branch current sample of the ultrasonic surgical device based on the stored current and voltage samples;
• compare the motional branch current sample to a target sample selected from a plurality of target samples that define a target waveform, the target sample selected based on the drive signal waveform sample;
• determine an amplitude error between the target sample and the motional branch current sample;
• and
• modify the drive signal waveform sample such that an amplitude error determined between the target sample and the motional branch current sample based on current and voltage samples associated with the modified drive signal waveform sample is reduced.