Amplifier circuits with ambient light cancelation

An integrated circuit, comprising:

• a first pin connectable to a photodiode to receive an input current from the photodiode;
• an amplifier connected to the first pin;
• a second pin connected to the amplifier to provide an output voltage indicative of the input current from the photodiode;
• a current source circuit connected between the first pin and the second pin;
• an analog-to-digital converter (ADC) circuit connected between the second pin and the current source circuit;
• and
• a controller configured to:
• during a first time period, measure a first current associated with the photodiode using the ADC circuit;
• and
• during a second time period, cause the current source circuit to provide a second current to the amplifier to at least partially cancel the first current.

An integrated circuit, comprising:

• a first pin connectable to a photodiode to receive an input current from the photodiode;
• an amplifier connected to the first pin;
• a second pin connected to the amplifier to provide an output voltage indicative of the input current from the photodiode;
• a current source circuit connected between the first pin and the second pin;
• a switch connected between the current source circuit and the second pin;
• an analog-to-digital converter (ADC) circuit connected between the second pin and the switch;
• and
• a controller configured to:
• during a first time period, measure a first current associated with the photodiode using the ADC circuit;
• and
• during a second time period, open the switch and cause the current source circuit to provide a second current to the amplifier to at least partially cancel the first current.