Patent ID: 7970125
Filing Date: 2011-06-28
Classification: H03F,H04M

Abstract:
1. An apparatus comprising: an operational amplifier having a first input coupled to receive a first current formed of an input current and an offset current; a first metal-oxide-semiconductor field effect transistor (MOSFET) device having a gate terminal coupled to an output of the operational amplifier, the first MOSFET device having a second terminal coupled to a second input of the operational amplifier; an output stack coupled to a first terminal of the first MOSFET device, the output stack comprising at least one cascoded device, wherein a first terminal of a first cascoded device is to provide an output current corresponding to a gain of the operational amplifier; a first resistor coupled between the first input of the operational amplifier and a first supply voltage; a second resistor coupled between the second terminal of the first MOSFET device and the first supply voltage, wherein a ratio of the first resistor to the second resistor sets the gain; a first Zener diode coupled between the first supply voltage and a gate terminal of a second cascoded device; and a second Zener diode coupled between the first terminal of the first cascoded device and a third resistor coupled to the gate terminal of the second cascoded device.