RF power transistor circuits
A radio frequency (RF) power transistor circuit includes a power transistor and a decoupling circuit. The power transistor has a control electrode coupled to an input terminal for receiving an RF input signal, a first current electrode for providing an RF output signal at an output terminal, and a second current electrode coupled to a voltage reference. The decoupling circuit includes a first inductive element, a first resistor, and a first capacitor coupled together in series between the first current electrode of the power transistor and the voltage reference. The decoupling circuit is for dampening a resonance at a frequency lower than an RF frequency.
1. A radio frequency (RF) power transistor circuit comprising:
a power transistor having a control electrode for receiving an RF input signal, and a current electrode for providing an RF output signal; and
a decoupling circuit comprising a first inductive element, a resistor, and a first capacitor coupled together in series between the current electrode of the power transistor and a ground terminal, wherein the first inductive element and the first capacitor form an inductor/capacitor circuit that has a resonance at a frequency below a passband range of frequencies for the RF power transistor circuit, and the resistor is configured to dampen the resonance of the inductor/capacitor circuit;
a node coupled to the current electrode, wherein the decoupling circuit is coupled between the node and the ground terminal; and
a D.C. blocking capacitor coupled in parallel with the decoupling circuit between the node and the ground terminal.
2. The RF power transistor circuit of claim 1 , further comprising:
a D.C. voltage pin coupled to the current electrode for providing a power supply voltage to the power transistor circuit.
3. The RF power transistor circuit of claim 2 , further comprising:
an output terminal coupled to the current electrode, wherein the D.C. voltage pin is coupled to the output terminal.
4. The RF power transistor circuit of claim 2 , further comprising:
a second inductive element coupled between the current electrode of the power transistor and a node, wherein the decoupling circuit is coupled between the node and the ground terminal, and wherein the D.C. voltage pin is coupled to the node.
5. The RF power transistor circuit of claim 4 , further comprising:
a third inductive element coupled between the D.C. voltage pin and the node, wherein a parallel inductance is formed by the second and third inductive elements.
6. The RF power transistor circuit of claim 1 , further comprising:
a second inductive element coupled between the current electrode of the power transistor and the node.
7. The RF power transistor circuit of claim 1 , further comprising:
a second inductive element coupled between the current electrode of the power transistor and a node, wherein the decoupling circuit is coupled between the node and the ground terminal.
8. The RF power transistor circuit of claim 7 , further comprising:
a D.C. blocking capacitor coupled in parallel with the decoupling circuit between the node and the ground terminal.
9. The RF power transistor circuit of claim 1 , further comprising:
an output terminal; and
a second inductive element coupled between the current electrode of the power transistor and the output terminal.
10. The RF power transistor circuit of claim 1 , wherein the decoupling circuit presents a high impedance path to RF signals within a passband range of frequencies between 1.6 gigahertz to 3.7 gigahertz.
11. The RF power transistor circuit of claim 1 , wherein the decoupling circuit provides a low frequency termination to ground for distortion products that develop due to envelope frequencies.
12. The RF power transistor circuit of claim 11 , wherein the resonance is 20 megahertz or less.
13. A radio frequency (RF) power transistor circuit comprising:
a power transistor having a control electrode for receiving an RF input signal, and a current electrode for providing an RF output signal; and
a decoupling circuit comprising
a first inductive element,
a resistor,
a first capacitor, wherein the first inductive element, the resistor, and the first capacitor are coupled together in series between the current electrode of the power transistor and a ground terminal, wherein the first inductive element and the first capacitor form an inductor/capacitor circuit that has a resonance at a frequency below a passband range of frequencies for the RF power transistor circuit, and the resistor is configured to dampen the resonance of the inductor/capacitor circuit, and wherein the resistor and the first inductor are coupled in series between second and third nodes, and
a second capacitor coupled between the second and third nodes in parallel with the resistor and the first inductor.
14. A radio frequency (RF) power transistor circuit comprising:
a power transistor having a control electrode for receiving an RF input signal, and a current electrode for providing an RF output signal; and
a first decoupling circuit comprising
a first inductive element,
a first resistor,
a first capacitor, wherein the first inductive element, the first resistor, and the first capacitor are coupled together in series between the control electrode of the power transistor and a ground terminal, wherein the first inductive element and the first capacitor form a first inductor/capacitor circuit that has a resonance at a frequency below a passband range of frequencies for the RF power transistor circuit, and the first resistor is configured to dampen the resonance of the first inductor/capacitor circuit, and wherein the resistor and the first inductor are coupled in series between second and third nodes, and
a second capacitor coupled between the second and third nodes in parallel with the resistor and the first inductor.
15. The RF power transistor circuit of claim 14 , further comprising:
an input terminal coupled to the control electrode of the power transistor, wherein the input terminal is configured to receive the first RF input signal; and
a D.C. voltage pin coupled to the control electrode for receiving a bias voltage.
16. A radio frequency (RF) power transistor circuit comprising: a power transistor having a control electrode for receiving an RF input signal, and a current electrode for providing an RF output signal;
a node coupled to the current electrode;
a first decoupling circuit comprising a first inductive element, a first resistor, and a first capacitor coupled together in series between the control electrode of the power transistor and a ground terminal, wherein the first inductive element and the first capacitor form a first inductor/capacitor circuit that has a resonance at a frequency below a passband range of frequencies for the RF power transistor circuit, and the first resistor is configured to dampen the resonance of the first inductor/capacitor circuit, wherein the second decoupling circuit is coupled between the node and the ground terminal;
a D.C. blocking capacitor coupled in parallel with the second decoupling circuit between the node and the ground terminal; and
a second decoupling circuit comprising a second inductive element, a second resistor, and a second capacitor coupled together in series between the current electrode of the power transistor and the ground terminal, wherein the second inductive element and the second capacitor form a second inductor/capacitor circuit that has a resonance at a frequency below the passband range of frequencies for the RF power transistor circuit, and the second resistor is configured to dampen the resonance of the second inductor/capacitor circuit.