US 6,252,460 B1 · FET balun transformer

Abstract

An inventive FET balun transformer uses a positive power supply alone, not a negative one, thus downsizing a device including the balun transformer. In the FET balun transformer, a voltage supplied from the positive power supply is divided by a voltage divider consisting of a pair of resistors. The gate of a first FET is biased at a positive voltage, which is obtained by getting the divided supply voltage further divided by a first resistor. The gate of a second FET is grounded with an AC grounded capacitor interposed therebetween and biased at a positive voltage, which is obtained by getting the divided supply voltage further divided by a second resistor. Thus, the gate and source of a third FET do not have to be set at a negative potential, but may be grounded directly and via a biasing resistor, respectively. As a result, no negative power supply is needed for the third FET and the single-ended signal received at the input terminal can be converted into differential signals, which will be output through output terminals, while using the positive power supply alone.

Claims6

Dependent claims

An FET balun transformer for converting a single-ended signal received at an input terminal into differential signals and then outputting the differential signals through first and second output terminals, respectively, the transformer comprising:

a first FET, the drain of which is connected to a positive power supply and the first output terminal, and the gate of which is connected to the input terminal;
a second FET, the drain of which is connected to the positive power supply and the second output terminal;
an AC grounded capacitor, one terminal of which is connected to the gate of the second FET and the other terminal of which is grounded;
a third FET, the drain of which is connected to the sources of the first and second FETs and the gate of which is grounded;
and
a series-resonant circuit, which is disposed between the first and second output terminals and causes a series resonance at a frequency twice higher than that of the single-ended signal received at the input terminal.

3 more elements

Dependencies are inferred from the claim text.

FET balun transformer

Life of this patent

FET balun transformer

Life of this patent

Abstract

Claims6