National Semiconductor’s ABiC IV BiCMOS process. All input and output ports of the LMX2216 are single-ended

Typical Application Block Diagram

Typical Characteristics

LNA (Continued)

                              LNA Gain vs Frequency with Supply                                                             LNA Noise Figure vs Frequency with

                             Voltage as a Parameter                                                                                Supply Voltage as a Parameter

Typical Characteristics (Continued)

MIXER

                 Mixer Gain (Double Sideband)                                                                      Mixer Gain (Double Sideband)

                 vs Frequency with Supply                                                                              vs Frequency with Temperature

                 Voltage as a Parameter                                                                                as a Parameter

Typical Characteristics

MIXER (Continued)

                              Mixer POUT vs PIN with Supply                                                                     Mixer POUT vs PIN with Supply

                              Voltage as a Parameter                                                                               Voltage as a Parameter

Typical Characteristics (Continued)

MIXER (Continued)

Mixer RFIN Return Loss vs Frequency with Supply

Voltage as a Parameter

Mixer IFOUT Return Loss vs Frequency with Supply

Voltage as a Parameter

FIGURE 3. Block Diagram of the LMX2216

Functional Description

THE LNA

The LNA is a common emitter stage with active feedback. This feedback network allows for wide bandwidth operation while providing the necessary optimal input impedance for low noise performance. The power down feature is implemented using a CMOS buffer and a power-down switch. The power down switch is implemented with CMOS devices. During power down, the switch is open and only leakage currents are drawn from the supply.

THE MIXER

The mixer is a Gilbert cell architecture, with the RF input signal modulating the LO signal and single ended output taken from the collector of one of the upper four transistors. The power down circuitry of the mixer is similar to that of the LNA. The power down switch is used to provide or cut off bias to the Gilbert cell.

Typical Low Noise Amplifier

TL/W/11814–14

FIGURE 4. Typical LNA Structure

A typical low noise amplifier consists of an active amplifying element and input and output matching networks. The input matching network is usually optimized for noise performance, and the output matching network for gain. The active element is chosen such that it has the lowest optimal noise figure, FMIN, an intrinsic property of the device. The noise figure of a linear two-port is a function of the source admittance and can be expressed by

F e FMIN a Rn [(GON b GG)2 a (BON b BG)2] GG

where G_G ^a jB_G ^e generator admittance presented to the input of the two port,

G_ON ^a jB_ON ^e generator admittance at which optimum noise figure occurs,

R_n ^e empirical constant relating the sensitivity of the noise figure to generator admittance.

)a

a sum of two sinusoids,

             AB     cos ((0

IEE 2 cos ((RF0RFa0LO0)LOt a) t wRFwRFawLOw)LO) one of which