Power amplifier
A power amplifier includes: a first transistor having a gate, a drain, and a source that is grounded; a second transistor having a gate, a drain, and a source that is connected to the drain of the first transistor; a capacitor connected between the gate of the second transistor and a grounding point; an idling current control circuit having a positive temperature coefficient and making an idling current flowing through the first transistor proportional to an ambient temperature; and a drain voltage control circuit having a positive temperature coefficient and making a drain voltage on the first transistor proportional to the ambient temperature.
1. A power amplifier comprising:
a first transistor having a gate, a drain, and a source that is grounded;
a second transistor having a gate, a drain, and a source that is connected to the drain of the first transistor;
a capacitor connected between the gate of the second transistor and a grounding point;
an idling current control circuit having a positive temperature coefficient and making an idling current flowing through the first transistor proportional to ambient temperature of the power amplifier; and
a drain voltage control circuit having a positive temperature coefficient and making a drain voltage on the first transistor proportional to the ambient temperature.
2. The power amplifier according to claim 1 , wherein the drain voltage control circuit supplies a voltage proportional to the ambient temperature to the gate of the second transistor.
3. The power amplifier according to claim 1 , wherein the drain voltage control circuit supplies a body voltage proportional to the ambient temperature to a substrate of the second transistor.
4. The power amplifier according to claim 1 , wherein the idling current control circuit includes:
a third transistor having a source that is grounded, and a gate and a drain that are connected to the gate of the first transistor; and
a current source having a positive temperature coefficient and supplying a current proportional to the ambient temperature to the gate and the drain of the third transistor.
5. A power amplifier comprising:
a first transistor having a gate, a drain, and a source that is grounded;
a second transistor having a gate, a drain, and a source that is connected to the drain of the first transistor;
a third transistor having a gate, a source connected to the drain of the first transistor, and a drain connected to the drain of the second transistor;
a capacitor connected between the gate of the second transistor and a grounding point;
an idling current control circuit having a positive temperature coefficient and making an idling current flowing through the first transistor proportional to ambient temperature of the power amplifier; and
a drain voltage control circuit having a positive temperature coefficient and making a drain voltage on the first transistor proportional to the ambient temperature.
6. The power amplifier according to claim 5 , wherein the drain voltage control circuit supplies a voltage proportional to the ambient temperature to the gate of the second transistor.
7. The power amplifier according to claim 5 , wherein the idling current control circuit includes:
a fourth transistor having a source that is grounded, and a gate and a drain that are connected to the gate of the first transistor; and
a current source having a positive temperature coefficient and supplying a current proportional to the ambient temperature to the gate and the drain of the fourth transistor.