Signal processing

A method of configuring a signal processing device to compensate for process and temperature variations deviating from a nominal process and temperature condition, the signal processing device comprising:

• i) a transconductance amplifier circuit portion having a respective voltage input and a current output, wherein the current output is dependent on the voltage input and a transconductance gain of said transconductance amplifier circuit portion;
• ii) a transimpedance amplifier circuit portion having a respective current input and a voltage output, wherein the voltage output is dependent on the current input and a transimpedance gain of said transimpedance amplifier circuit portion, wherein said transconductance and transimpedance amplifier circuit portions are arranged in series;
• iii) a bias circuit portion comprising first and second transistors configured such that:
• a gate terminal and a drain terminal of the first transistor are connected to a gate terminal of the second transistor and to a reference current input configured to receive a reference current from a proportional-to-absolute-temperature current source;
• a drain terminal of the second transistor is connected to a current supply input of the transconductance amplifier;
• a source terminal of the first transistor is connected to a node via a first resistor;
• and
• a source terminal of the second transistor is connected to said node via a second resistor, wherein the second resistor is trimmable;
• and
• iv) a feedback circuit portion connected between the input and output of the transimpedance amplifier, said feedback circuit portion comprising a third resistor, wherein the third resistor is trimmable;
• wherein a resistance of the first resistor is a predetermined value, said predetermined value being a resistance of the trimmable third resistor at the nominal process and temperature condition;
• wherein the method comprises:
• varying a respective resistance of each of the trimmable second and third resistors such that a ratio between the resistances of said trimmable second and third resistors is constant.