US Patent 9083287 Electronic biasing circuit for constant transconductance

An electronic biasing circuit provides a DC bias voltage to a circuit to be biased. The biasing circuit has a first transistor and a second transistor. A gate of the first transistor is connected to a gate of the second transistor and supplies the DC bias voltage. A source of the first transistor is connected to a supply reference voltage. A source of the second transistor is connected to the supply reference voltage via a resistor element. The currents flowing through the first and second transistor are forced to be equal. A third transistor is connected in series with the first transistor and a fourth transistor is connected in series with the second transistor. Currents flowing through the third and fourth transistors are forced to be equal.