BACKGROUND

Many radio frequency front-end architectures use amplifiers to combine, split, and isolate various parts of the signal path to support multiple modes of operation. For example, amplifiers able to turn off and isolate a particular signal path can be used to reconfigure an in-phase and quadrature signal receiver into a real signal only receiver to reduce power consumption, to select particular receiver channels for mufti-channel radios, to select particular clock signals or local oscillator signals between multiple sources, and as a replacement for conventional switches in transmitter and receiver paths in time division multiplexing systems. However, parasitic capacitances of transistors can cause signal leakage between signal paths, which makes isolating one signal path from another difficult at millimeter (mm) wave frequencies. Further, conventional signal multiplexing schemes can experience device reliability issues.

SUMMARY

In some implementations, an amplifier comprises six transistors. The first transistor is coupled to a first input, and the second transistor is coupled to a second input. The third transistor is coupled to the first transistor and to a first output, and the fourth transistor is coupled to the second transistor and to a second output. The fifth transistor is coupled to the first and third transistors and to the second output, and the sixth transistor is coupled to the second and fourth transistors and to the first output. Characteristics of the fifth transistor such as threshold voltage, geometry, rotation, and biasing are chosen to match the corresponding characteristics of the fourth transistor. Similarly, characteristics of the sixth transistor are chosen to match the corresponding characteristics of the third transistor.

In some implementations, the fifth and sixth transistors are biased to be on while the amplifier operates in an isolation mode and biased to be off while the amplifier does not operate in the isolation mode. In some examples, the fifth and sixth transistors comprise metal oxide semiconductor field effect transistors and are biased such that a gate to drain voltage of the fifth and sixth transistors does not cause a gate oxide breakdown in the fifth and sixth transistors.

