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 first power transistor having a first control electrode for receiving a first RF input signal, and a first current electrode for providing a first RF output signal;
a second power transistor having a second control electrode for receiving a second RF input signal, and a second current electrode for providing a second RF output signal;
a first node electrically coupled to the first and second current electrodes; and
a decoupling circuit comprising a first inductive element, a resistor, and a first capacitor coupled together in series between the first node and a voltage reference.
2. The RF power transistor circuit of claim 1 , 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.
3. The RF power transistor circuit of claim 2 , wherein the resistor is configured to dampen the resonance of the inductor/capacitor circuit.
4. The RF power transistor circuit of claim 2 , wherein the resonance is 20 megahertz or less.
5. The RF power transistor circuit of claim 1 , further comprising:
a first D.C. blocking capacitor coupled between the first node and the voltage reference.
6. The RF power transistor circuit of claim 5 , further comprising:
a second inductive element coupled between the first current electrode of the first power transistor and the first D.C. blocking capacitor.
7. The RF power transistor circuit of claim 6 , further comprising:
a second node between the second inductive element and the first D.C. blocking capacitor; and
a third inductive element coupled between the first node and the second node.
8. The RF power transistor circuit of claim 7 , further comprising:
a second D.C. blocking capacitor coupled between the first node and the voltage reference.
9. The RF power transistor circuit of claim 8 , further comprising:
a fourth inductive element coupled between the second current electrode of the second power transistor and the second D.C. blocking capacitor.
10. The RF power transistor circuit of claim 9 , further comprising:
a third node between the fourth inductive element and the second D.C. blocking capacitor; and
a fifth inductive element coupled between the first node and the third node.
11. The RF power transistor circuit of claim 1 , further comprising:
an RF output terminal;
a second inductive element coupled between the first current electrode of the first power transistor and the RF output terminal; and
a third inductive element coupled between the second current electrode of the second power transistor and the RF output terminal.
12. The RF power transistor circuit of claim 1 , further comprising:
a first RF output terminal;
a second RF output terminal;
a second inductive element coupled between the first current electrode of the first power transistor and the first RF output terminal; and
a third inductive element coupled between the second current electrode of the second power transistor and the second RF output terminal.
13. 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.
14. 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.
15. The RF power transistor circuit of claim 1 , wherein a resistance value of the resistor is in a range of 0.5 ohms to 5 ohms.
16. The RF power transistor circuit of claim 1 , wherein a capacitance value of the first capacitor is in a range of 10 nano Farads to 1,000 nano Farads.
17. The RF power transistor circuit of claim 1 , wherein an inductance value of the first inductive element is in a range of 0.1 nano Henrys to 3 nano Henrys.