Patent ID: 6717450
Filing Date: 2004-04-06
Classification: G01R

Abstract:
An active load circuit comprising:a current source; a current sink; a current switching diode bridge including a plurality of Schottky diodes, an input node for receiving an output voltage of a pin of a device under test, a reference node for receiving a buffered reference voltage, and current source and current sink nodes respectively connected to said current source and said current sink; a pin output voltage buffer having an input for receiving said pin output voltage and an output for providing a buffered pin output voltage; a reference circuit responsive to a fixed reference voltage and said buffered pin output voltage for providing a controlled reference voltage which tracks said buffered pin output voltage so as to be two Schottky diode voltage drops less than said buffered pin output voltage when said buffered pin output voltage is greater than said fixed reference, and two Schottky diode voltage drops greater than said buffered pin output voltage when said buffered pin output voltage is less than said fixed reference; and a reference voltage buffer receiving said controlled reference voltage at a buffer input and for providing said buffered reference voltage.