Control circuit driven by a differential input voltage and method for controlling same
AssigneeGain Technology Corporation
InventorThomas A. Somerville
Life of this patent
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Abstract
The present invention teaches a variety of output stages for amplifying high speed signals while keeping distortion low and using a low supply voltage. The invention includes the use of dual complementary signal paths that include a complementary push-pull output stage. Bias circuits are used to keep the paths symmetrical and positive feedback is used to oppose output loading effects.
Claims39
A control circuit driven by a differential input voltage, the control circuit suitable for driving a complementary push-pull common-emitter output stage, the control circuit comprising:
- a first stage having a first single-ended output and a first differential input coupled to the differential input voltage, the first stage operable to generate a first current signal at the single-ended output, the first current signal being substantially proportional to the differential input voltage, the first stage including a first transconductance device having an input that is the first differential input and a folded cascade amplifier coupled in parallel with the first differential pair of transistors, the folded cascade amplifier including a Schottky diode;
- and
- a second stage having a second single-ended output and a second differential input coupled to the differential input voltage, the second stage operable to generate a second current signal at the single-ended output, the second current signal being substantially proportional to the differential input voltage;
- wherein the first and second stages are connected in parallel, the first and second current signals providing a substantially symmetrical signal pair for driving a complementary push-pull output stage.
An output stage amplifier comprising:
- a control circuit driven by a differential input voltage, the control circuit including:
- a first input stage having a first single-ended output and a first differential input coupled to the differential input voltage, the first input stage operable to generate a first current signal at the single-ended output, the first current signal being substantially proportional to the differential input signal, the first input stage including a first transconductance device, comprising a first differential pair of transistors and a folded cascade amplifier including a Schottky diode, the folded cascade amplifier being coupled in parallel with the first differential pair of transistors, and the first input stage having an input that is the first differential input;
- a second input stage having a second single-ended output and a second differential input coupled to the differential input voltage, the second stage operable to generate a second current signal at the single-ended output, the second current signal being substantially proportional to the differential input voltage,
- wherein the first and second input stages are connected in-parallel, the first and second current signals providing a substantially symmetrical signal pair;
- and
- a complementary push-pull output stage including first and second push-pull amplifiers each having an output, the first amplifier driven by the first input stage and the second push-pull amplifier driven by the second input stage, the outputs of the first and second push-pull amplifiers being coupled together, such that two complementary signal paths are provided from input to output.
A method for controlling a complementary push-pull output stage having first and second push-pull amplifiers each having an input and an output, an output of the complementary push-pull output stage being formed by coupling of the outputs of the first and second push-pull amplifiers, the method comprising the act of providing substantially symmetrical input signals to the first push-pull input and the second push-pull input, whereby:
- a first input stage having a first single-ended output and a first differential input coupled to a differential input voltage, the first input stage operable to generate a first current signal at the single-ended output, the first current signal being substantially proportional to the differential input signal, the first input stage including a first transconductance device, comprising a first differential pair of transistors and a folded cascade amplifier including a Schottky diode, the folded cascade amplifier being coupled in parallel with the first differential pair of transistors, and the first input stage having an input that is the first differential input;
- and
- a second input stage having a second single-ended output and a second differential input coupled to the differential input voltage, the second stage operable to generate a second current signal at the single-ended output, the second current signal being substantially proportional to the differential input voltage,
- wherein the first and second input stages are connected in parallel, the first and second current signals providing a substantially symmetrical signal pair for driving the complementary push-pull output stage, thus providing two signal paths from input to output.
Dependencies are inferred from the claim text.