Methods and apparatus for power amplifier transformers
An example apparatus includes a first transformer winding having a first proximal end and a first distal end and a second transformer winding having a second proximal end and a second distal end, the first proximal end having a first distance from the second proximal end and the first distal end having a second distance from the second distal end, the first distance less than the second distance.
1 . An apparatus comprising:
a first transformer including:
a first transformer winding having an output at a first proximal end and a first center tap at a first distal end; and
a second transformer including:
a second transformer winding having an output at a second proximal end and a second center tap at a second distal end, the first proximal end having a first distance from the second proximal end and the first distal end having a second distance from the second distal end, the first distance less than the second distance.
2 . The apparatus of claim 1 , wherein:
the first transformer winding includes:
a first output and a second output, wherein the second output is at the first proximal end; and
a first number of turns; and
the second transformer winding includes:
a third output and a fourth output, wherein the fourth output is at the second proximal end, the first output coupled to third output, and the second output coupled to the fourth output; and
a second number of turns.
3 . The apparatus of claim 2 , wherein:
the first transformer includes a third transformer winding having a third number of turns equal to the first number of turns of the first transformer winding; and
the second transformer includes a fourth transformer winding having a fourth number of turns equal to the second number of turns of the second transformer winding, wherein the first and second transformer windings are secondary windings and the third and fourth transformer windings are primary windings.
4 . The apparatus of claim 3 , wherein:
the third transformer winding includes a first input; and
the fourth transformer winding includes a second input.
5 . The apparatus of claim 2 , wherein:
the first transformer winding includes:
a first vertex located at the first output; and
a second vertex located at the first center tap, wherein a first centerline is defined by the first vertex and the second vertex; and
the second transformer winding includes:
a third vertex located at the second output; and
a fourth vertex located at the second center tap, wherein a second centerline is defined by the third vertex and the fourth vertex; and
a third centerline extending between the first transformer winding and the second transformer winding and bisecting the first output and the second output, the first centerline and the third centerline forming a first acute angle, the second centerline and the third centerline forming a second acute angle.
6 . The apparatus of claim 1 , wherein:
the first transformer winding includes a first number of turns;
the second transformer winding includes a second number of turns; and
the first transformer includes a first primary winding having turns, and the second transformer includes a second primary winding having turns, in which a sum of the turns of the first and second primary windings is a third number of turns, wherein a sum of the first number of turns and the second number of turns is equal to the third number of turns.
7 . The apparatus of claim 1 , wherein:
the output of the first transformer winding is a first output, and further including a second output;
the output of the second transformer winding is a fourth output, and further comprising a third output, the first output coupled to the third output, and the second output coupled to the fourth output;
the first transformer includes a third transformer winding having a first input at a first end and having a second end; and
the second transformer includes a fourth transformer winding having a third end coupled to the second end and a second input at a fourth end.
8 . The apparatus of claim 7 , further comprising:
a primary center tap coupled to the second and third ends; and
a trace coupled to the primary center tap.
9 . The apparatus of claim 8 , wherein the trace has a width, the width to tune a second harmonic frequency to adjust a signal at one or both of the first and second inputs.
10 . A system comprising:
a driver stage configured to output a signal;
a transformer circuit coupled to an output of the driver stage and including:
a first transformer winding having a first proximal end and a first distal end; and
a second transformer winding having a second proximal end and a second distal end, the first proximal end having a first distance from the second proximal end and the first distal end having a second distance from the second distal end, the first distance less than the second distance; and
an output stage coupled to the first and second transformer windings and configured to increase a power of the signal.
11 . The system of claim 10 , wherein the system comprises:
a biasing circuit;
wherein the first transformer winding includes a first center tap located at the first distal end and coupled to the biasing circuit; and
wherein the second transformer winding includes a second center tap located at the second distal end and coupled to the biasing circuit.
12 . The system of claim 11 , wherein the biasing circuit is a DC biasing circuit.
13 . The system of claim 10 , wherein:
the first transformer winding and the second transformer winding are secondary windings, the transformer circuit further including at least one primary winding having a first number of turns, the secondary windings having a combined number of turns equal to the first number of turns.
14 . The system of claim 10 , wherein:
the first transformer winding includes a first output and a second output, the second output is at the first proximal end; and
the second transformer winding includes a third output and a fourth output, the fourth output at the second proximal end, the first output coupled to third output and the second and fourth outputs coupled together.
15 . The system of claim 10 , wherein:
the first transformer winding includes:
a first output located at the first proximal end;
a first vertex located at the first output;
a first center tap located at the first distal end; and
a second vertex located at the first center tap, wherein a first centerline is defined by the first vertex and the second vertex; and
the second transformer winding includes:
a second output located at the second proximal end;
a third vertex located at the second output;
a second center tap located at the second distal end; and
a fourth vertex located at the second center tap, wherein a second centerline is defined by the third vertex and the fourth vertex; and
a third centerline extending between the first transformer winding and the second transformer winding and bisecting the first output and the second output, the first centerline and the third centerline forming a first acute angle, the second centerline and the third centerline forming a second acute angle.
16 . The system of claim 15 , wherein the first centerline and the second centerline form a right angle.
17 . The system of claim 10 , wherein the transformer circuit is implemented by complimentary metal-oxide semiconductors (CMOS) compatible stacked-type on-chip transformers.
18 . The system of claim 10 , wherein the transformer circuit further includes:
a third transformer winding having a first input at a first end and a second end;
a fourth transformer winding having a third end and a second input at a fourth end; and
a primary center tap coupled to the second and third ends.
19 . The system of claim 18 , further including a trace coupled to the primary center tap.
20 . The system of claim 19 , wherein the trace has a width, the width to tune a second harmonic frequency to adjust a signal at one or both of the first and second inputs.