Abstract: An impedance matching circuit (10) matches the impedance of a load (19) coupled to an RF amplifier (12) to that of the RF amplifier (12). The impedance matching circuit (10) samples a transmitted signal from the RF amplifier (12) and a reflected signal from the load (19). The amplitude and the phase of the sampled reflected signal are compared with those of the sampled transmitted signal to calculate the impedance mismatch. A control logic circuit (80) adjusts the capacitance and inductance values of variable capacitance (23; 27) and inductance (35) elements in the impedance matching circuit (10), thereby matching the impedance of the load (19) to that of the RF amplifier (12).

Abstract: A protection element (10) protects a battery pack (36) from potential faulty conditions in a load (38). The protection element (10) includes a switch (12), a control FET (14), and three resistors (16, 18, and 22). Under normal operating conditions, the switch (12) is conductive and the control FET (14) is non-conductive. If a short circuit is detected, the controller (14) becomes conductive and turns off the switch (12). The switch (12) remains non-conductive until the load (38) is disconnected from the protection element (10). The protection element (10) further includes a temperature sensor (24) that turns off the switch (12) at high temperatures and a current limiting element (28) that imposes an upper limit on the current flowing through the protection element (10). Control signals can be applied to the gate electrodes of the switch (12) and the control FET (14) to modulate the current in the protection element (10).