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TQ9222

Dual-Band TDMA LNA/Downconverter IC

TriQuint Semiconductor 

Introduction

The TQ9222 3V RFIC Downconverter is designed specifically

for dual-band TDMA applications. The TQ9222 contains two

separate LNA+Mixer circuits to handle both the 800 MHz

cellular band and the 1900 MHz PCS band. The IF frequency

range covers 70 to 140 MHz. Most of the ports are internally

matched to 50 Ω simplifying the design and keeping the number

of external components to a minimum. Separate supply voltage

connections provide the required flexibility for dual-band

operation.

Operation: Please refer to the applications test circuit above.

General Description

Low Noise Amplifier (LNA)

The LNA sections of the TQ9222 consist of two cascaded

common source FETs (see Fig 1). Each LNA is designed to

operate on supply voltages from 3V to 5V. The main differences

between the high and low band LNAs are the bias circuits. The

source terminal of the first stage has to be grounded very close

to the pin (pin 1 for PCS band and pin 12 for cellular band). This

will avoid a significant gain reduction due to degeneration. The

LNA requires a matching circuit on the input to provide a good

noise, gain and return loss performance. The output is close to

50 Ω for direct connection to a 50 Ω image stripping filter.

Fig 1. TQ9222

Simplified

Schematic of

LNA Section

LNA

in

BIAS

Vdd

LOAD

BIAS

LNA

out

Fig 1. LNA Sections

Cellular Band Mixer

The cellular band mixer of the TQ9222 is implemented by a

common source depletion FET. The mixer is designed to

operate on supply voltages from 3V to 5V. An on-chip buffer

amplifier simplifies direct connection of the LO input to a

commercial VCO at drive levels down to -7dBm. The common-

TQ9222

Data Sheet

gate LO buffer provides a good input match, and supplies the

voltage gain necessary to drive the mixer FET gate. The "open-

drain " IF output allows for flexibility in matching to various IF

frequencies and filter impedances (see Fig. 2).

Fig 2. Cellular Band Mixer

LO Bias and

Mixer LO Tuning

Input

Mixer RF

Input

Mixer IF

Output

PCS Band Mixer

The PCS band mixer section of the TQ9222 is a balanced

mixer with a single ended output. This balanced mixer topology

minimizes the LO leakage out of the RF and IF ports thereby

giving excellent LO suppression (see Fig. 3)

Mixer LO

Input

Mixer RF

Input

Vdd

Mixer IF

Output

Fig 3. PCS Band Mixer

Low Noise Amplifier Application

To obtain the best possible combination of performance and

flexibility, the high and low band LNAs were designed to be

used with off-chip input impedance matching. Based on the

system requirements, the designer can make several

performance trade-offs and select the best impedance match for

the particular application.

For additional information and latest specifications, see our website: www.triquint.com

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