Patent ID: 8531241

Claim:
In a differential amplifier, a method for process, voltage, temperature (PVT) stable transfer function calibration, the method comprising: providing a differential amplifier including a first field effect transistor (FET), a second FET, a first variable resistance gain resistor between the drain (D) of the first FET and a first dc supply voltage, a second variable resistance gain resistor between the drain of the second FET and the first dc supply voltage, a variable resistance degeneration resistor between the source (S) of the first FET and the source of the second FET, a variable capacitance degeneration capacitor between the source of the first FET and the source of the second FET, a first current source connected between the source of the first FET and a second dc supply voltage, and a second current source connected between the source of the second FET and the second dc supply voltage; disconnecting the degeneration capacitor; supplying a differential input signal to the first and second FET gates in a first frequency band having a low frequency (f L ) and a high frequency (f H ); selectively adjusting values for the first gain resistor, second gain resistor, and the degeneration resistor; and, measuring a differential output signal with a flat amplitude transfer function in the first frequency band, responsive to the differential input signal and adjusted values.