US Patent 7319220 Trans-impedance amplifier with offset current

A trans-impedance amplifier receives an input current and is operable to generate an output voltage responsive to the input current. The amplifier is responsive to an increased range of input currents and has a wide bandwidth. The amplifier includes an input stage having a first and a second transistor and is configured to receive the input current. The amplifier includes an output stage coupled to the input stage and having a third and a fourth transistor. A variable resistor is coupled to the output stage to adjust the amount of current in the output stage. A variable current source is coupled to the output stage and is operable to adjust the amount of current in the output stage. A output driver, which is coupled to the output stage, includes at least another transistor. The output driver is operable to provide the output voltage and is operable to reduce the output impedance of the amplifier.