Patent ID: 8736358
Filing Date: 2014-05-27
Classification: G05F

Abstract:
1. A current source providing an output current with a fixed current range, the current source comprising: a bias circuit, for providing a first voltage, which is weighted with a first tunable coefficient and providing a second voltage, which is weighted with a second tunable coefficient; a resistor, having a tunable resistance, the resistor determining a bias current according to a voltage difference between the first and the second voltages; a current mirror, for generating the output current according to the bias current; and a controller, for achieving a voltage-current coefficient, which is defined by a difference of the output current per the first voltage, the controller further selectively having the voltage-current coefficient configured with different values by means of adjusting the tunable resistance and one of the first tunable coefficient and the second tunable coefficient, and keeping the bias current and the output current within a fixed current range; wherein the bias circuit further comprises: a first node and a second node, wherein one of the first voltage and the second voltage is provided on the second node and is directly connected to the resistor; an operational amplifier, having a first input end and a second input end respectively receiving a first reference voltage and coupled to the first node, and having an output node; a transistor, having a first terminal and a second terminal respectively receiving a second reference voltage and coupled to the second node, and having a control terminal coupled to the output node; a first resistor, coupled between the first and the second node; and a second resistor, having a first terminal and a second terminal respectively coupled to the first node and receiving a ground reference.