Patent
Constant current r.f. generator
Reads0
Chats0
TLDR
In this article, a high gain differential amplifier which compares a d.c. voltage derived from the r.f. output of the system against a highly stable voltage reference is used to control the voltage via a transformer to the drain of a FET operated as a Class C amplifier in saturated mode.Abstract:
The present invention achieves constant voltage at radio frequencies to drive a constant voltage to constant current converter, by employing a tightly coupled d.c. feedback loop to control the voltage via a transformer to the drain of a FET operated as a Class C amplifier in the saturated mode whereby among other advantages, the amplifier can withstand, without damage, very high VSWRs. Control is affected by a high gain differential amplifier which compares a d.c. voltage derived from the r.f. output of the system against a highly stable d.c. voltage reference. A controller, responding to the output of the differential amplifier causes a first level of voltage to be applied to the drain of the FET when the system is not loaded and causes a second voltage varying between said first level and a higher level when the system is loaded. In the lower voltage condition the controller is effectively removed from the system so that it does not have to drop a high voltage to a low voltage; the low voltage being supplied effectively from a separate source.read more
Citations
More filters
Patent
Resistively heated cutting and coagulating surgical instrument
TL;DR: In this paper, a resistively heated thermally cutting and coagulating surgical instrument with bipolar output ports and a bipolar cable is presented, where the temperature is maintained at a value restricted to a temperature below curie temperature.
Patent
High power self-regulating heater
TL;DR: In this paper, an improved performance ferromagnetic self-regulating heater is presented, where one or more layers of non-magnetic material is added to the Ferromagnetic layer in such a way that the power factor of the heater is significantly increased above its value in the absence of at least one of the layers.
Patent
Generating electromagnetic fields in a self regulating temperature heater by positioning of a current return bus
TL;DR: A self-redulanting heater includes an electricallyconductive substrate (11), having a magnetic surface layer (13) of one skin depth, folded 180 degrees to define two heater sections joined by a fold section as discussed by the authors.
Patent
Regulated-current power supply and methods for resistively-heated surgical instruments
Dennis J. Denen,Albert E. Weller +1 more
TL;DR: In this paper, a power supply for use with resistively-heated surgical instruments is provided, wherein the desired operating conditions of the surgical instrument are determined by a setpoint determination circuit in combination with a set-point indicator element.
Patent
Endoscopic instrument with auto-regulating heater and method of using same
TL;DR: In this paper, an instrument for use in endoscopic surgery is described, which has a heating element with a working surface for providing hemostasis at an auto-regulated temperature, and a tapered edge for providing thermally enhanced cutting and a non-stick coating for operating the instrument at low auto-regulation temperatures.
References
More filters
Patent
Circuit to protect rf output amplifier against mismatch damage
TL;DR: In this article, a mismatch protection circuit is proposed to protect power output transistors of a communications transmitter from damaging excessive reflected power, as might occur when the antenna is disconnected or broken, which circuit continuously monitors and compares parameters indicative of forward and reflected power or VSWR and when there is excessive mismatch, instantaneously cuts back the dc power delivered to the transistors to a safe low level, but a level sufficient for continued cutback operation of the protection circuit, when and for so long as the excessive mismatch continues.
Patent
Programmable RF power regulator (stabilizer)
TL;DR: In this article, a regulator circuitry (stabilizer) for controlling the output of an RF generator according to a programmable input signal is described, and a feedback control circuit monitors and controls the power output stage so that the desired output level is maintained at a constant level.
Patent
Low level modulation system for a radio transmitter
TL;DR: In this article, a low level modulation circuit for use in a radio transmitter obviates the need for an audio transformer device heretofore required for high signal level modulation of the final stages of a multistage radio frequency amplifier by modulating an initial amplifier stage using a conditioned, low-level modulation signal, but yet eliminates additional distortion and noise imposed upon the modulated audio signal by the initial and intermediate amplification stages, through the use of a single, negative feedback circuit.