Trimmable current source
AssigneeMotorola, Inc.
InventorDavid M. Susak
Life of this patent
Estimating the term…
Abstract
A JFET circuit generates an adjustable current having a temperature coefficient proportional to I.sub.DSS where I.sub.DSS is the drain current of a JFET when its source and gate are shorted. The JFET has a source terminal coupled to a source of supply voltage. An adjustable resistor is coupled between the gate and source terminals of the JFET. A reference current is supplied to the resistor, which reference current is proportional to the JFET's pinch-off voltage. The desired current appears at the drain of the JFET.
Claims2
A circuit for generating an adjustable current having a temperature coefficient proportional to that of I.sub.DSS where I.sub.DSS is a drain current of a JFET when its soruce and gate terminals are shorted, comprising:
- a first JFET having a source terminal coupled to a source of supply voltage, a drain terminal for conducting said current, and having a gate terminal;
- an adjustable resistor coupled between said gate terminal and said source terminal;
- and
- a current source coupled to said resistor for causing a current to flow through said resistor so as to develop a voltage across said gate and source terminals, wherein said current source generates a current proportional to the pinch-off voltage of said first JFET.
Dependencies are inferred from the claim text.