Input amplifier with improved power supply rejection
View Patent ↗An input amplifier for power amplifier control circuitry includes an input, an output, a power supply voltage, a ground, a differential amplifier and a double folded cascode and conversion stage. The differential amplifier is connected to the input, to the power supply voltage and to the ground. The differential amplifier provides a differential output. The double folded cascode and conversion stage is connected to the differential amplifier, to the ground and to the power supply voltage. The double folded cascode and conversion stage converts the differential output to a single-ended signal. The double folded cascode and conversion stage is optimized to prevent variation in the power supply voltage from propagating to the output.
1. An input amplifier for power amplifier control circuitry comprising:
an input;
an output;
a power supply voltage;
a ground;
a differential amplifier connected to the input, to the power supply voltage and to the ground, the differential amplifier providing a differential output; and,
a double folded cascode and conversion stage connected to the differential amplifier, to the ground and to the power supply voltage, the double folded cascode and conversion stage converting the differential output to a single-ended signal, the double folded cascode and conversion stage being optimized to prevent variation in the power supply voltage from propagating to the output, wherein the double folded cascode and conversion stage includes:
a first current source connected to the power supply voltage;
a second current source connected to the power supply voltage;
a first transistor connected to the first current source and to a first differential output of the differential amplifier;
a second transistor connected to the second current source and to a second differential output of the differential amplifier;
a third transistor connected to the first current source;
a fourth transistor connected to the second current source and to the output;
a fifth transistor connected to the third transistor and to the ground; and,
a sixth transistor connected to the output and to the ground.
2. An input amplifier as in claim 1 :
wherein the first current source is a first bipolar transistor having an emitter connected to the power supply voltage, having a collector connected to the first transistor and having a base connected to a current source bias voltage; and,
wherein the second current source is a second bipolar transistor having an emitter connected to the power supply voltage, having a collector connected to the second transistor and having a base connected to the current source bias voltage.
3. An input amplifier as in claim 1 :
wherein the first transistor is a first bipolar transistor having a collector connected to the first current source, having an emitter connected to the first differential output and having a base connected to a first base bias voltage;
wherein the second transistor is a second bipolar transistor having a collector connected to the second current source, having an emitter connected to the second differential output and having a base connected to the first base bias voltage;
wherein the third transistor is a third bipolar transistor having an emitter connected to the collector of the first transistor, having a collector and having a base connected to a second base bias voltage;
wherein the fourth transistor is a fourth bipolar transistor having an emitter connected to the collector of the second transistor, having a collector connected to the output and having a base connected to the second base bias voltage;
wherein the fifth transistor is a fifth bipolar transistor having a collector connected to the collector of the third transistor, having an emitter connected to the ground and having a base connected to the collector of the fifth transistor and,
wherein the sixth transistor is a sixth bipolar transistor having a collector connected to the collector of the fourth transistor, having an emitter connected to the ground and having a base connected to the collector of the fifth transistor.
4. An input amplifier as in claim 3
wherein the first current source is a seventh bipolar transistor having an emitter connected to the power supply voltage, having a collector connected to the collector of the first transistor and having a base connected to a current source bias voltage; and,
wherein the second current source is an eighth bipolar transistor having an emitter connected to the power supply voltage, having a collector connected to the collector of the second transistor and having a base connected to the current source bias voltage.
5. An input amplifier as in claim 4 wherein the differential amplifier includes:
a third current source connected to the power supply voltage;
a ninth bipolar transistor having an emitter connected to the third current source, having a collector providing the first differential output, and having a base connected to a positive component of the input;
a tenth bipolar transistor having an emitter connected to the third current source, having a collector providing the second differential output, and having a base connected to a negative component of the input;
a fourth current source connected to the collector of the ninth bipolar transistor and to the ground; and,
a fifth current source connected to the collector of the tenth bipolar transistor and to the ground.
6. A power amplifier module comprising:
a power supply voltage;
a ground;
a power amplifier;
a feedback amplifier circuit connected to the power amplifier;
an input voltage conditioning circuit, the input voltage conditioning circuit including an input amplifier, wherein the input amplifier includes:
an input,
an output;
a differential amplifier connected to the input, to the power supply voltage and to the ground, the differential amplifier providing a differential output, and
a double folded cascode and conversion stage connected to the differential amplifier, to the ground and to the power supply voltage, the double folded cascode and conversion stage converting the differential output to a single-ended signal, the double folded cascade and conversion stage being optimized to prevent variation in the power supply voltage from propagating to the output, wherein the double folded cascode and conversion stage includes:
a first current source connected to the power supply voltage;
a second current source connected to the power supply voltage;
a first transistor connected to the first current source and a first differential output of the differential amplifier;
a second transistor connected to the second current source and a second differential output of the differential amplifier;
a third transistor connected to the first current source;
a fourth transistor connected to the second current source and to the output;
a fifth transistor connected to the third transistor and to the ground; and,
a sixth transistor connected to the output and to the ground.
7. A power amplifier module as in claim 6 :
wherein the first current source is a first bipolar transistor having an emitter connected to the power supply voltage, having a collector connected to the first transistor and having a base connected to a current source bias voltage; and,
wherein the second current source is a second bipolar transistor having an emitter connected to the power supply voltages having a collector connected to the second transistor and having a base connected to the current source bias voltage.
8. A power amplifier module as in claim 6 :
wherein the first transistor is a first bipolar transistor having a collector connected to the first current source, having an emitter connected to the first differential output and having a base connected to a first base bias voltage;
wherein the second transistor is a second bipolar transistor having a collector connected to the second current source, having an emitter connected to the second differential output and having a base connected to the first base bias voltage;
wherein the third transistor is a third bipolar transistor having an emitter connected to the collector of the first transistor, having a collector and having a base connected to a second base bias voltage;
wherein the fourth transistor is a fourth bipolar transistor having an emitter connected to the collector of the second transistor, having a collector connected to the output and having a base connected to the second base bias voltage;
wherein the fifth transistor is a fifth bipolar transistor having a collector connected to the collector of the third transistor, having an emitter connected to the ground and having a base connected to the collector of the fifth transistor; and,
wherein the sixth transistor is a sixth bipolar transistor having a collector connected to the collector of the fourth transistor, having an emitter connected to the ground and having a base connected to the collector of the fifth transistor.
9. A power amplifier module as in claim 8 :
wherein the first current source is a seventh bipolar transistor having an emitter connected to the power supply voltage, having a collector connected to the collector of the first transistor and having a base connected to a current source bias voltage; and,
wherein the second current source is an eighth bipolar transistor having an emitter connected to the power supply voltage, having a collector connected to the collector of the second transistor and having a base connected to the current source bias voltage.
10. A power amplifier module as in claim 9 wherein the differential amplifier includes:
a third current source connected to the power supply voltage;
a ninth bipolar transistor having an emitter connected to the third current source, having a collector providing the first differential output, and having a base connected to a positive component of the input;
a tenth bipolar transistor having an emitter connected to the third current source, having a collector providing the second differential output, and having a base connected to a negative component of the input;
a fourth current source connected to the collector of the ninth bipolar transistor and to the ground; and,
a fifth current source connected to the collector of the tenth bipolar transistor and to the ground.
11. A power amplifier module as in claim 10 wherein the feedback amplifier circuit includes:
a current sensor resistor connected between the power supply voltage and a current input to the power amplifier;
a first resistor having a first end connected to the current input to the power amplifier and having a second end; and,
a feedback amplifier having a positive input connected to the second end of the first resistor, having a negative input connected to the input voltage conditioning circuit and having an output connected to a control input of the power amplifier.
12. A power amplifier module as in claim 10 wherein the input voltage conditioning circuit additionally includes:
a first voltage divider resistor having a first end connected to the power supply voltage;
a second voltage divider resistor having a first end connected to the ground;
a field effect transistor having a drain connected to a second end of the first voltage divider resistor, having a source connected to a second end of the second voltage divider resistor and to the negative component of the input of the input amplifier and having a gate connected to the output of the input amplifier; and,
a threshold voltage source connected between the ground and the source of the field effect transistor.
13. A power module circuit as in claim 12 wherein the feedback amplifier circuit includes:
a current sensor resistor connected between the power supply voltage and a current input to the power amplifier;
a first resistor having a first end connected to the current input to the power amplifier and having a second end; and,
a feedback amplifier having a positive input connected to the second end of the first resistor, having a negative input connected to the drain of the field effect transistor and having an output connected to a control input of the power amplifier.