Control of input bias current modulation in amplifiers

An amplifier comprising:

• a pre-driver;
• a separation circuit coupled to the pre-driver;
• first and second current-replication transistors coupled to the separation circuit, the first and second current-replication transistors having respective control terminals;
• first replica-current subtraction circuitry having an input current terminal coupled to the control terminal of the first current-replication transistor and an output current terminal coupled to the pre-driver;
• and
• second replica-current subtraction circuitry having an input current terminal coupled to the control terminal of the second current-replication transistor and an output current terminal coupled to the pre-driver, wherein:
• a current terminal of the first current-replication transistor is driven with a first error current component to generate a first replica base current component that approximates an error-modulation component of a first pre-driver base current;
• and
• a current terminal of the second current-replication transistor is driven with a second error current component to generate a second replica base current component that approximates an error-modulation component of a second pre-driver base current.

An amplifier comprising:

• a pre-driver;
• a separation circuit coupled to the pre-driver;
• first and second current-replication transistors coupled to the separation circuit, the first and second current-replication transistors having respective control terminals;
• first replica-current subtraction circuitry having an input current terminal coupled to the control terminal of the first current-replication transistor and an output current terminal coupled to the pre-driver;
• and
• second replica-current subtraction circuitry having an input current terminal coupled to the control terminal of the second current-replication transistor and an output current terminal coupled to the pre-driver, wherein:
• the first replica-current subtraction circuitry includes first and second NPN transistors having commonly coupled base terminals that are also coupled to a collector terminal of the first NPN transistor, the collector of the first NPN transistor forming the input current terminal of the first replica-current subtraction circuitry;
• and
• the second replica-current subtraction circuitry includes first and second PNP transistors having commonly coupled base terminals that are also coupled to a collector terminal of the first PNP transistor, the collector of the first PNP transistor forming the input current terminal of the second replica-current subtraction circuitry.

An amplifier comprising:

• a first stage including:
• a pre-driver,
• a separation circuit coupled to the pre-driver, and first and second current-replication transistors coupled to the separation circuit, the first and second current-replication transistors having respective control terminals;
• and
• a second stage preceding the first stage, the second stage including:
• replica-current subtraction circuitry coupled to the control terminals of the first and second current-replication transistors, wherein the replica-current subtraction circuitry is configured to subtract first and second replica current components that approximate error-modulation components of respective first and second base currents of the pre-driver and that are injected from the first stage into the second stage.

A method comprising:

• separating first and second error current components from other current components in a pre-driver of an amplifier;
• driving a first current-replication transistor of the amplifier with the first separated error current component;
• generating, in response to the driving of the first current-replication transistor, a first replica base current component that approximates an error-modulation component of a first pre-driver base current;
• driving a second current-replication transistor of the amplifier with the second separated error current component;
• generating, in response to the driving of the second current-replication transistor, a second replica base current component that approximates an error-modulation component of a second pre-driver base current;
• subtracting the first replica base current component from the first pre-driver base current;
• and
• subtracting the second replica base current component from the second pre-driver base current.