Combination offset voltage and bias current auto-zero circuit
View Patent ↗A circuit with an input acquisition loop and an output acquisition loop is used to compensate for the input offset voltage and bias current errors of an operational amplifier.
1. A circuit comprising:
an operational amplifier; and
an input acquisition loop; and
an output acquisition loop; wherein the output of the operational amplifier goes through the input acquisition loop in a first phase and through the output acquisition loop in a second phase and wherein the circuit compensates for the input offset voltage and bias current errors of the operational amplifier; and
wherein a first resistor is switched in across the inputs of the operational amplifier in the first phase.
2. The circuit of claim 1 , wherein the operational amplifier is a current-mode-feedback amplifier (CMFA) amplifier.
3. The circuit of claim 1 , wherein the operational amplifier is a transimpedance amplifier.
4. The circuit of claim 1 , wherein a voltage drop across a resistor in the output acquisition loop compensates for the input offset voltage of the operational amplifier.
5. The circuit of claim 1 , further including a photodiode that produces an input current to the circuit.
6. The circuit of claim 5 , wherein the photodiode is used to detect information from an optical medium.
7. The circuit of claim 6 , wherein the optical medium is an optical disk.
8. The circuit of claims 5 , wherein the current from the photodiode is directed towards different inputs of the operational amplifier in the first and second phase.
9. The circuit of claim 1 , wherein the input acquisition and output acquisition loop include buffers.
10. A circuit comprising:
an operational amplifier;
an input acquisition loop; and
an output acquisition loop; wherein the output of the operational amplifier goes through the input acquisition loop in a first phase and through the output acquisition loop in a second phase and wherein the circuit compensates for the input offset voltage and bias current errors of the operational amplifier; wherein, in the first phase, current from a photodiode flows through an resistor in parallel with the inputs of the operational amplifier and through one of the inputs of the operational amplifier; and wherein, in the second phase current from the photodiode flows to the other of the inputs of the operational amplifier.
11. The circuit of claim 10 , wherein the operational amplifier is a current-mode-feedback amplifier (CMFA) CMFA amplifier.
12. The circuit of claim 10 , wherein the operational amplifier is a transimpedance amplifier.
13. The circuit of claim 10 , wherein a voltage drop across a resistor in the output acquisition loop compensates for the input offset voltage of the operational amplifier.
14. The circuit of claim 13 , wherein the photodiode is used to detect information from an optical medium.
15. The circuit of claim 14 , wherein the optical medium is an optical disk.
16. The circuit of claim 10 , wherein the input acquisition and output acquisition loop include buffers.
17. The circuit of claim 1 , wherein the output acquisition loop includes a second resistor that matches the first resistor.